How Do I Backwash a Sand Filter in My Fiberglass Pool?

Fiberglass pools provide years of memories for pool owners. The crystal-clear water brings joy and relaxation. However, keeping your water clear involves more than just routine cleaning and chemical adjustments. According to independent pool dealers in our network, backwashing the sand filter is an often overlooked yet crucial pool maintenance step for those with this type of filtration system. Let’s explore the importance of backwashing, some frequently asked questions, and how it’s done.

About Pool Filters

There are three available types of pool filters: sand, diatomaceous earth (DE), and cartridge. Sand filters are a very common form of swimming pool filtration, and they are particularly good at catching microscopic particles like algae and phosphates. Sand filters require very little maintenance, but the sand may need replacing every two to four years or so.

What is backwashing?

 

Backwashing a sand filter is a maintenance procedure that cleans the filter and ensures it operates efficiently. Over time, as water pumps through the sand filter, debris and particles are trapped by the sand, removing them from the pool water. This process gradually accumulates dirt and debris in the filter, which can decrease efficiency and lead to cloudy pool water.

Backwashing reverses the water flow through the sand filter. Instead of dirty water coming in and clean water going out, clean water is pumped backward through the filter. This reverse flow lifts and flushes the trapped debris from the sand bed and the filter through a waste line or drain.

During backwashing, the sand within the filter loosens, allowing the trapped debris to be expelled. After backwashing, the filter is returned to its normal operation mode and ready to filter pool water again. This process is essential for maintaining the filter’s ability to clean the pool water effectively and should be performed regularly as part of the pool’s maintenance routine.

Why is backwashing important? 

Backwashing keeps your filter functioning properly and clear of debris. It also helps to keep your water clear. You can religiously add chlorine to the chlorinator, check its settings, sweep down the pool walls, empty skimmer baskets, vacuum dirt and debris from main drains, do water tests, maintain the correct water level, and clean the steps going into the pool. Regardless, your pool water will get cloudy if you forget to clean the filter. Nobody wants that.

What happens if I don’t backwash my sand filter?

If you don’t backwash your sand filter, you may notice your water getting cloudy or debris making its way to the surface of your pool water. As stated above, you can do all other essential maintenance tasks, but none will replace the need for backwashing.

How do I know if I need to backwash my sand filter?

You will need to check your filter’s pressure gauge. When clean, your filter will have a typical reading you should note. You’ll know it’s time to backwash once the gauge reaches 8 to 10 pounds (psi) above your baseline reading. Your water may also look cloudy or dirty when the filter is ready to be backwashed. 

What is the proper way to backwash a sand filter? 

Proper Way to Backwash Sand Filter

  1. Turn the filter system off. 
  2. Remove, empty, and replace the skimmer basket.
  3. Attach a backwash hose to your filter’s backwash port.
  4. Turn your multi-port valve to Backwash. (Make sure you never turn the multi-port valve handle while the pool filter is on and running.)
  5. Turn your filter system back on. Water should now be flowing out the backwash port and through the hose.
  6. Let the water run for about two minutes, or until the water runs clear in the site glass.
  7. Turn the filter system off again.
  8. Turn the multi-port valve to Rinse
  9. Turn the filter system back on, and rinse the filter for about 30 seconds to one minute.
  10. Turn the system off.
  11. Turn the multi-port valve to Filter.
  12. Turn the system back on.

Potential Issues and How to Avoid Them

 

  • Sand in your pool. If you notice sand in your pool during or after backwashing, then you might have cracked off laterals or piping inside the filter. You may also have too much sand in the filter. The space from the filter’s top to the sand line’s beginning is called “freeboard.” This space is essential to prevent sand from exiting the filter during backwash.
  • Too much of a good thing. While backwashing is essential, it is possible to backwash a sand filter too often and too much. As mentioned previously, how often you backwash should be based on the readings from your pressure gauge, as too much (or too little) backwashing can lead to some undesirable outcomes. During backwashing, turn the hose off as soon as your water runs clear. Prolonged backwashing of your sand filter can cause “channeling.” Channeling occurs when channels develop down the sides inside the filter. When this happens, water can bypass the sand altogether, defeating your sand filter’s purpose. 

As with all aspects of your pool’s operation and maintenance, please follow the sand filter’s instructions carefully, as each model varies slightly. You will likely find directions on the filter itself. Your filter and your pump are the backbones of your pool, and it’s essential to pay equal attention to both of them. A failure of either will cause problems and cost you money. You should consult a pool professional if you have any pool maintenance concerns.

When is the Best Time to Open My Pool?

It’s that time of the year! Spring is finally here! The weather is warming up, and the summer swim season is almost upon us. You may have slept since the last pool opening, or this may be your first season as a pool owner, and you’re wondering when and how to open your pool. As a fiberglass pool shell manufacturer, Thursday Pools doesn’t install or maintain pools. However, we stay informed through independent pool dealers throughout the country. In this post, we’ll share their best pool maintenance tips, including advice on opening your pool. 

 

The Best Time to Open Your Pool

 

Your pool opening and closing schedule will vary based on where you live. Once you’ve made it past the danger of a damaging freeze, it’s time to kick it into gear. The sooner you open your fiberglass inground pool, the sooner you’ll have fun in the sun with all your family and friends. While you may have already scheduled a pool maintenance pro to help you learn how to open your inground fiberglass pool, you can still do some things to get the ball rolling.

 

How to Reopen an Inground Pool

 

  1. Check your water level. When wondering what is the first thing you should do when opening a pool, you need to check that your water level is up to mid-way on your skimmer before you remove your pool cover. Even with your pool tightly covered, your water level will likely lower over the winter. Groundwater levels are often at their highest in the spring (especially if you have a lot of snow in the winter). If groundwater pressure becomes unequalized, it can cause catastrophic damage to your fiberglass inground pool.

 

  1. Remove your pool cover. After your water level is correct, pump off any water on the pool cover. Be sure to pump AWAY from your pool so you’re not just adding more groundwater around it. If you have a leaf blower, you might use that to blow off any leaves or other debris. After that, the process depends on which kind of pool cover you have. 
  • Automatic pool covers. You may have heard us tout the virtues of automatic pool covers before, and hopefully, you have one. Your pool opening may be easier if you do. Be sure to open it gradually with your touchpad, checking that your cover isn’t sticking or crooked in the tracks as you go. 
  • Standard winter covers: Your winter cover needs to be adequately removed, cleaned and sanitized to store away for your fall pool closing. Be sure to check with your cover’s manufacturer for removal instructions, as each differs. Removing your pool cover the wrong way can cause unwanted debris to fall into and contaminate your water, making it more challenging to balance your water.

 

  1. Check your equipment. Once your water is at the proper level, your cover is off, and you’ve skimmed off any large debris, you can turn on and check your pool equipment. Pumps, filters, filter media, skimmer baskets, and lights sitting idle in the elements all winter might need tuning up or replacing. The time to find that out is before the swimming season kicks off. Most professional pool opening services will perform a complete check and alert you to any problem areas or necessary repairs. If all is working well, leave your pump on and let the water circulate for at least 12 hours.

 

  1. Check your pool water chemistry. Once your water has had a chance to circulate, you’ll need to test it to see where you’re starting with water balance. Water balance can be very challenging at the start of the season. Whether or not you have a pool service pro open your pool, you might need help getting your water balanced after a long winter. Many swimming pool professionals provide a free, computerized water analysis that tests for many more water balance factors than a standard home test kit. It’s always a good idea to have your pool water professionally tested regularly to keep track of all the necessary components of balanced and healthy water. If you properly balance your water when opening your pool, you’ll have an easier time keeping your water chemistry balanced throughout the swim season. 

 

  1. Give the pool a spring cleaning. Give the pool a spring cleaning. Start by scrubbing the pool walls. Be sure to use a soft brush or sponge when cleaning your pool walls, and avoid abrasives such as sandpaper and steel wool, which will damage the finish of your pool. After you’ve given the walls a good cleaning, it’s time to vacuum. Begin in the shallow end and work your way down the slope of the pool. Thoroughly clean around the steps and other crevices where debris can accumulate.

 

  1. Inspect your safety equipment and pool accessories. Your handrails and lifesavers need to be swim-ready by the time you are. Take time in the spring to inspect, maintain, or replace safety equipment, fiberglass pool accessories, and even outdoor furniture so that you can relax poolside on opening day!

Take some steps now to get as many tasks checked off your list as possible so you can prepare to open your inground fiberglass pool. Have a safe, fun, relaxing pool season. It’s almost time to float around and enjoy.

How to Protect Your Pool Water Balance During the Off-season

 

As the vibrant days of summer fade into the crisp air of autumn, fiberglass pool owners face the critical task of preparing their pools for the off-season. However, the upcoming period of dormancy does not equate to a halt in maintenance efforts. Instead, the off-season requires a strategic approach to ensure your pool water is neither corrosive nor scaling and will be ready for the next swimming season. Smart homeowners must understand the essential steps for monitoring the pool’s water chemistry balance during the colder months to safeguard against potential damage that winter can bring.

 

Water Chemistry Challenges in the Off-Season

Fiberglass pools, celebrated for their durability and longevity, are not immune to all the challenges of changing seasons. Fiberglass pool shells are generally resilient against winter conditions thanks to their flexibility, which can withstand stress from freezing temperatures. However, harsh winter conditions can still threaten the water balance and the pool surface if you do not properly winterize the pool. The risk of damage escalates during winter when colder water temperatures can render the water more aggressive. This aggressiveness primarily stems from the water’s chemistry balance shifting with temperature changes, potentially leading to issues that can compromise the integrity of your pool’s finish.

 

Seasonal Cleaning and Preparation

The first step in your off-season maintenance routine should be thoroughly cleaning your pool. End-of-season cleaning includes wiping down the waterline with a soft brush to eliminate any buildup of debris, sunscreen, body oils, and other contaminants that may have accumulated over the swimming season. Brush all pool surfaces, paying extra attention to corners and steps where algae and bacteria might accumulate. Remove all leaves, debris, and dirt from the water using a skimmer, and vacuum the pool thoroughly to eliminate any settled particles or algae. A clean pool goes beyond attractive aesthetics to create a stable foundation for your off-season water balance efforts.

 

The Role of a Pool Cover

Investing in a high-quality pool cover offers multiple benefits throughout the year, with its importance magnified during the off-season. A pool cover acts as a barrier against debris, reduces water evaporation, and helps maintain the pool’s water chemistry balance by minimizing external influences. 

 

Especially important for households with children or pets, a properly secured winter pool cover can also prevent accidental falls into the pool. Safety covers can withstand a person’s weight, providing an extra layer of protection when the pool is not in use. More than a convenience, a pool cover offers peace of mind and ensures your pool remains clean, sealed, and safe throughout the winter.

 

Enjoy the Benefits of Proactive Off-Season Maintenance

The effort you put into off-season maintenance directly impacts the longevity and condition of your fiberglass pool. By taking steps to clean your pool, adjust its water chemistry for the cold, periodically check its balance, and secure it with a pool cover, you protect your investment and make for an easier and more efficient opening in the spring.

 

A proactive approach ensures your pool remains a source of enjoyment and relaxation for many years without extensive repairs or adjustments when the swim season arrives. Embrace the off-season as an opportunity to ensure your fiberglass pool’s continued health, beauty, and enjoyment.

 

Frequently Asked Questions About Off-Season Pool Water Chemistry

 

Why is water chemistry so important during the off-season?

Cold water can shift your pool’s chemistry and become more aggressive. Keeping pH, total alkalinity, and calcium in check, and routine use of a stain and scale product, helps protect your fiberglass surface and equipment throughout the winter months.

 

Do I need to clean my pool before closing for the season?

Yes. A thorough cleaning is essential. Brush all surfaces, skim, and vacuum to eliminate algae, dirt, and debris. A clean pool sets the stage for stable water chemistry all winter long.

 

What role does a pool cover play in off-season maintenance?

A high-quality pool cover keeps debris, dirt, and leaves out of the water, reduces evaporation, and helps preserve your pool’s chemical balance. Covers make winter care easier and spring openings faster.

 

Should I check my pool’s water chemistry during the winter?

Yes. Weather permitting, check the water’s balance periodically. Cold water’s chemistry can still shift over time, and making small adjustments ensures it remains stable. Regular checks prevent surprises at spring opening and help extend the life and beauty of your fiberglass pool.

 

What are the most common mistakes pool owners make during the off-season?

The biggest mistakes include failing to balance water chemistry for colder temperatures, skipping a thorough cleaning before closing, and not using a quality pool cover. Neglecting these steps can lead to algae growth, staining, scaling, or corrosion that makes spring opening more difficult and costly.

 

How does proper off-season care make spring opening easier?

When you clean, balance, and cover your pool correctly before winter, you prevent debris buildup and chemical imbalances. That means fewer surprises—like cloudy water, stains, or equipment issues—when you reopen. A proactive approach saves time, reduces costs, and helps you start swimming sooner in the spring.

What Does Routine Fiberglass Pool Maintenance Look Like?

Owning a fiberglass pool brings with it the benefits of reduced upkeep demands and the guarantee of continuous enjoyment during the warmer months. Yet, it’s crucial to recognize that this ease of ownership is complemented by the need for consistent maintenance, particularly in maintaining balanced pool water chemistry, to ensure your pool remains a radiant and inviting space to spend time with your family and friends. This post examines what routine fiberglass pool maintenance entails and guides you through a plan to keep your pool in perfect harmony throughout the swimming season.

 

Starting the Season Right

Opening your fiberglass pool marks the commencement of the swimming season and sets the stage for a season of fun and relaxation. Once you open your pool, commit to conducting daily tests to adjust your pool’s chemistry until the water’s Langelier Saturation Index (LSI) value is balanced (-0.30 to +0.30). This crucial first step ensures your pool water is neither too corrosive nor scaling, protecting the integrity and appearance of the fiberglass gel coat.

 

Maintaining Chlorine Levels

Once the LSI is in balance, the next step is to add sanitizer to maintain chlorine levels within a safe range of 1 to 3 parts per million (ppm). This range is optimal for disinfecting the pool without damaging the fiberglass surface. Monitoring and adjusting chlorine levels is a fundamental aspect of routine maintenance that keeps the water clear, clean, and safe for swimmers.

 

Weekly Checks and Adjustments

Your pool’s water chemistry can quickly fluctuate even after establishing a balanced baseline due to various events such as changes in swimmer load, weather conditions, organic debris, water evaporation and more. Perform weekly tests to ensure ongoing water balance, checking the chlorine, pH, alkalinity, and other factors contributing to the LSI. These regular check-ins help catch and correct minor imbalances before they become bigger issues.

 

Water Level and Filtration Maintenance

Maintaining the pool’s water level is another vital aspect of routine care. The water level should always be halfway to the top of the skimmer window to ensure efficient filtration and circulation. Regularly check and clean the filter and skimmer baskets to prevent clogs and maintain proper function. Additionally, vacuuming your pool to remove debris and sediment keeps the water clearer and reduces the strain on your pool’s filtration system.

 

Gentle Cleaning for Long-Lasting Shine

The non-porous gelcoat surface of fiberglass pools is highly stain-resistant, making cleaning a breeze. A soft microfiber cloth, sponge, or pool brush with nylon bristles should suffice. Some household cleaners contain harsh chemicals unsuitable for fiberglass pool surfaces and may cause damage over time. Always use cleaners specifically designed for fiberglass pools as aggressive cleaning agents can damage the gelcoat, leading to unnecessary wear and repair costs. Metal scrapers or putty knives can gouge or scratch the fiberglass when used to remove debris or scale. Also avoid using highly abrasive tools such as wire and stiff bristle brushes or steel wool. 

 

The Value of Prevention

In pool maintenance, an ounce of prevention is worth a pound of cure. Regular, proactive care keeps your pool looking and performing its best and extends the life of your investment. Fortunately, the inherent durability and ease of care associated with fiberglass pools mean that maintaining balanced water chemistry requires less effort than you might think. Test kits and tools such as the Orenda LSI calculator smartphone application can help by quickly providing direction on how to properly balance your pool water.

 

Understanding Low Maintenance Isn’t Maintenance-Free

While fiberglass pools are celebrated for their low maintenance needs, it’s important to remember that “less maintenance” doesn’t mean “maintenance-free.” The foundation of a healthy, long-lasting pool is balanced water chemistry, achieved through frequent and routine testing, precise adjustments, and regular cleaning. By embracing these responsibilities, you’ll ensure your pool remains a beautiful source of joy, relaxation, and pride.

Routine fiberglass pool maintenance, centered around balanced water chemistry, is the cornerstone of a healthy, beautiful pool. By beginning the season with thorough testing and adjustments, maintaining chlorine levels, weekly checks, keeping the pool clean, and proactively managing the water balance, you can enjoy a trouble-free swimming experience. 

 

Five Essential Steps to Maintain Your Pool’s Finish

For many homeowners, the benefit of reduced maintenance responsibilities is influential in their decision to install a fiberglass pool in their backyard. The non-porous surface of a fiberglass pool significantly lessens the likelihood of algae growth and reduces the demand for chemicals to maintain water balance. This inherent characteristic of fiberglass pools substantially contributes to their appeal, offering homeowners more time to enjoy their aquatic sanctuary with less laborious upkeep. However, it’s crucial to understand that “lower maintenance” does not equate to “maintenance-free.” Maintaining your pool’s vibrant, smooth finish is just as important as keeping the water clear and inviting. While the allure of crystal-clear water is undeniable, the unseen balance of water chemistry plays a crucial role in preserving the integrity and appearance of your pool. 

 

Step 1: Use a Stain and Scale Control Product Regularly

 

Even well-balanced water can carry minerals that deposit on your pool’s surface, leading to staining or scale buildup. A reliable stain and scale control product helps prevent fiberglass pool discoloration with chelating agents that can effectively shield your pool from calcium. In our experience, products like SC-1000 by Orenda and Scale & Stain Eliminator by Pool Stain Removers work well and should be part of your regular pool maintenance routine.

 

Step 2: Maintain Chlorine Levels Between 1-3 ppm

 

Chlorine protects your pool from harmful bacteria and algae. While chlorine is essential, too much can harm your pool’s finish. Keep free chlorine between 1 and 3 ppm. Beware of exceeding 5 ppm, as high chlorine levels can cause irreversible damage to your pool’s surface, leading to discoloration and degradation of the gelcoat.

 

Step 3: Avoid Calcium Hypochlorite

 

While calcium hypochlorite is common in various pool contexts for shock treatments, it poses risks for fiberglass pool surfaces due to its propensity to elevate pH levels and deliver a high dose of free chlorine. Liquid chlorine is a preferable alternative, offering a safer means to manage pool hygiene without the associated risks of calcium hypochlorite. Nevertheless, vigilance is required to prevent the adverse effects of excessive chlorine, ensuring the pool’s surface remains pristine.

 

Step 4: Keep pH Between 7.2 and 7.4

 

Maintaining a pH range between 7.2 and 7.4 keeps your chlorine effective and protects the pool’s surface. A pH above 7.8 can contribute to scaling and discoloration, while a pH that’s too low can lead to etching. Regular testing and adjustments help keep this critical pool maintenance parameter within range.

 

Step 5: Maintain Calcium Hardness Below 120 ppm

 

Fiberglass pools don’t need the same high calcium levels as concrete pools. Keeping calcium hardness less than 120 ppm helps prevent scale buildup and maintains the beauty of your surface finish. Do not add calcium-based products. If your water’s calcium hardness is greater than 120 ppm, use a chelating stain and scale control product to prevent scaling and discoloration.

 

Bonus Tip: Don’t Assume Your Pool Pros Know it All!

 

The pool maintenance industry is constantly evolving, with new products and refined best practices emerging regularly. As a pool owner, staying informed about these developments is beneficial to ensure your pool receives the best care possible.

 

Engage with your pool maintenance professionals and inquire whether they are familiar with specific parameters for fiberglass pools. Fiberglass pools are unique, and maintenance pros should treat them as such.

 

By following these five essential tips and staying on top of your water chemistry, you’ll protect your pool’s beauty and performance for years to come. Pool ownership is a journey. When you have the right knowledge, it’s a journey you can enjoy with confidence.

 

Looking for more information on fiberglass pool care? Explore Thursday Pools’ Ultimate Fiberglass Pool Maintenance Guide for a thorough look at everything you need to know.

 

And if you’re ready for personalized advice, connect with a local independent Thursday Pools dealer near you.

 

Frequently Asked Questions About Maintaining a Fiberglass Pool Finish

 

How do I protect my fiberglass pool’s finish?

Test your water often, keep chlorine between 1-3 ppm, maintain pH between 7.2-7.4, and use a stain and scale control product that chelates calcium. These steps prevent discoloration, scaling, and surface damage.

 

Why should I avoid calcium hypochlorite in a fiberglass pool?

Calcium hypochlorite raises pH and delivers a strong chlorine dose that can harm your pool’s gelcoat. Use liquid chlorine instead to sanitize safely.

 

What calcium hardness level works best for fiberglass pools?

Keep calcium hardness below 120 ppm. Higher levels can cause scale buildup and discoloration. Use a stain and scale control product that chelates calcium if you have naturally hard water with high calcium hardness, such as SC-1000 by Orenda or Scale & Stain Eliminator by Pool Stain Removers.

 

Does clear water always mean my pool water is balanced?

No. Water can look crystal clear but still be corrosive or scaling. Always test and adjust based on the LSI balance, especially as water temperature changes.

 

Should I rely on a pool service professional for water balance?

Stay informed and ask questions. Fiberglass pools require specific care, and not every pool professional knows the latest best practices. Double-check your pool’s water chemistry balance yourself regularly.

Examining the Elements Involved in Factoring LSI

Maintaining balanced pool water chemistry in your fiberglass pool is truly a balancing act. Each of the six factors that calculate the Langelier Saturation Index (LSI) can ebb and flow, although some are more reactionary and volatile than others. While maintaining all six factors may feel like a juggling act, understanding what they are, how they interact, and their impact on your pool is critical to keeping the LSI balanced and your water in equilibrium.

 

The Critical Role of pH

pH, or “potential of hydrogen,” is the most critical variable in water chemistry balance. While alterations of any involved equation variables can affect your water balance, a change in pH can have ten times the effect compared to other LSI factors

pH levels indicate water’s acidity or basicity. They range from 0 to 14, with 0 being very acidic, 7 being neutral, and 14 being very basic. Chlorine and other sanitizers will only remain effective and function correctly within specific pH ranges—namely, the range between 7.2 and 7.4 deemed ideal for swimming pools. Hydrochloric or muriatic acid can lower high pH levels, while a low-pH pool will need an alkaline boost from sodium carbonate. 

The best thing an owner can do for the health and safety of their pool and its frequent swimmers is to regularly test the pH and other chemical levels. Daily testing and checks before and after each use are recommended and will help you become more familiar with how various factors, including some outside your control, affect your pH and overall LSI levels. 

 

Total Alkalinity

Alkalinity is often called “the yin to pH’s yang,” as the two are related. Alkalinity measures water’s capacity to withstand changes in pH. In fiberglass pools, recommended total alkalinity levels range from 80 to 120 parts per million.

Low alkalinity makes water corrosive, causing stains and etching on your pool’s surface. Water will become depository if alkalinity rises above the recommended range for fiberglass pools (120 ppm). As a result, pool surface scaling occurs and a white cloudy film may appear, clogging filters and reducing circulation.

 

Total Dissolved Solids (TDS)

As the name implies, total dissolved solids (TDS) include chemicals or anything other than calcium that remains after water evaporates. These solids can include salts, metals, minerals, and other organic materials that have entered and dissolved within the pool water. We recommend that the TDS level be no higher than 1,500 ppm (or 1,000 ppm above safe salt level in saltwater pools). A high TDS level can lead to algae blooms, scaling, or other pool stains.

 

Cyanuric Acid (Chlorine Stabilizer)

Cyanuric acid (CYA) will prevent the sun’s ultraviolet rays from decomposing free chlorine in your pool water. Levels between 30 and 50 ppm are recommended, but higher levels don’t necessarily mean better results. If the cyanuric acid level reaches 100 ppm or above, chlorine’s effectiveness at killing bacteria and algae is compromised.

 

Calcium Hardness

A lower calcium hardness level in your pool water results in a softer and silkier it will feel on swimmers’ skin. Calcium hardness is also essential for maintaining water cleanliness and equipment operation. Regulated calcium hardness of less than 120 ppm will help keep pool materials looking and working their best. When calcium hardness is too low, the water becomes aggressive and corrosive. When too high, pH levels raise, leading to cloudy water, surface discoloration, and filter-clogging calcium deposits.

 

Temperature

The temperature factor is the only non-chemical component of water chemistry balance and your pool’s LSI. Utilizing a pool heater will make your temperature factor much easier to control. Many swimmers enjoy a “bathwater” feel and temperature, but water warmer than 82 degrees Fahrenheit can encourage bacteria or algae growth. Calcium deposits form more quickly in warmer water, while a too-cool pool makes it easier for water to begin corroding equipment.

Parents of infants and young children should consider keeping temperatures slightly higher into the upper 80s. However, a pool used primarily for exercise or competitive swim training should skew lower, between 77 and 82 degrees Fahrenheit. A good general rule for many pool owners is aiming for a water temperature between 77 degrees and the mid-80s. Keeping a constant temperature will help prevent bacteria and algae growth and improve the efforts of chlorine, saltwater, or other pool sanitation measures.

 

Every Factor is Important

Many pool owners and even pool service professionals habitually test for pH and chlorine, and occasionally they check the alkalinity. However, this approach ignores many critical LSI factors. Although they do not tend to change as rapidly, You should also regularly test calcium hardness, CYA, and TDS. By testing all six factors in your pool water, you will have a more clear and complete understanding of its LSI and water balance.

 

How Do I Balance My Pool Water Using LSI?

Balancing your pool water is essential for maintaining its clarity, safety, and longevity, especially for fiberglass pool owners. While pool water chemistry balance may seem complex, modern tools like the Orenda Technologies LSI Calculator have simplified the testing and adjustment process. This blog post will guide you through using Orenda’s app to achieve optimal water balance in your pool, ensuring it stays in beautiful condition without needing a degree in chemistry. We’ve included step-by-step instructions, complemented by screen-capture images, to make the process as straightforward as possible.

Editor’s Note: There are available alternatives to the Orenda app. Thursday Pools and Orenda have no relationship other than sharing a desire to help fiberglass pool owners properly maintain their water chemistry. If you want to get even more informed on water balance and related topics, check out Orenda’s library of educational videos, tutorials, and other resources. 

Step 1: Download the Orenda App

The journey to balanced pool water begins with a simple download of the Orenda app, available on both iOS and Android platforms. This app significantly simplifies pool chemistry, particularly focusing on the Langelier Saturation Index (LSI), making it an indispensable tool for pool owners.

 

Orenda App

 

Step 2: Input Your Pool Details

Once you have downloaded and opened the app, the first step is to input your pool’s specific details, such as the volume of your pool in gallons and the water temperature, which are critical for accurate calculations. The app’s user-friendly interface guides you through entering these initial details.

 

Step 3: Enter Current Water Chemistry Levels

The next step involves inputting the current levels of various water chemistry variables that influence your pool’s LSI.

Water Chemistry Levels

These include: 

  • Water temperature
  • pH level
  • Calcium Hardness
  • Total Alkalinity
  • Cyanuric Acid stabilizer
  • Total Dissolved Solids

You’ll find a section on the left-hand side of the app dedicated to entering these values. Precise measurements at this stage are crucial for accurately assessing your pool’s water balance. 

Also, note that the app includes levels for Chlorine and Phosphates. While these values don’t affect the LSI, they are essential in maintaining a healthy and safe pool.

 

Step 4: Adjusting for Optimal LSI

After entering your pool’s details and current chemistry levels, the real magic begins. The app allows you to tweak and adjust the values on the right-hand side of the screen to see how changes can affect your pool’s LSI. 

The goal is to adjust these levels until you achieve a desired LSI value within the optimal range of -0.3 to +0.3. Note that for saltwater pools, we recommend a slightly tighter range of -0.2 to +0.2 to account for the unique chemistry of saltwater systems.

Optimal LSI

The app’s LSI indicator is highlighted in different colors depending on the status. 

  •   Over +0.30 is coded PURPLE, meaning your water can cause scaling on your equipment and gelcoat surface. 
  • -0.30 to +0.30 is coded GREEN to indicate the ideal LSI balance. 
  • -0.30 to -0.01 is YELLOW, meaning you’re close to balance but not quite there. 
  • < -0.30 is coded RED to alert you to corrosive water that can damage your pool equipment and gelcoat surface.

The ideal target is as close to zero as possible. This interactive feature allows you to experiment with different adjustments to understand how each factor may affect your pool’s overall balance.

 

 

Calculate and Correct

Step 5: Calculate and Correct

After adjusting your inputs to reach the ideal LSI range, hitting the “Calculate” button creates a customized list of actions and products needed to balance your pool water. It tells you what needs to be adjusted and recommends specific chemicals and quantities to achieve the desired balance. This step eliminates guesswork, ensuring you use the right products in the right amounts.

Step 6: Implement Recommendations

With a tailored action plan, the final step is implementing the app’s recommendations. Whether adjusting the pH, adding calcium hardness increaser, or balancing total alkalinity, follow the guidelines to bring your pool water into harmony.

Why Use the Orenda App?

Simplifies Complex Calculations

The Orenda app demystifies the complexity of water chemistry, breaking it down into simple and manageable steps. This guidance ensures that pool owners can maintain their pool’s health without needing deep technical knowledge.

Saves Time and Money

By providing precise recommendations, the app helps pool owners avoid over- or under-treating their pool, saving money on chemicals and preventing potential damage to the pool’s surface or equipment.

Enhances Pool Enjoyment

Regularly using the Orenda app to balance your pool water means clearer, safer water and a more enjoyable swimming experience for you and your family. It also extends the lifespan of your pool by preventing damage and other issues related to imbalanced water.

Balancing your pool water using the LSI doesn’t have to be daunting. With the Orenda Technologies LSI Calculator, achieving and maintaining optimal water balance is easier and more intuitive than ever. By following the simple steps outlined above and taking advantage of the app’s smart recommendations, you can ensure your pool remains an enjoyable oasis for years to come.

 

What is LSI?

LSI and Fiberglass Pool Chemistry

The Langelier Saturation Index (LSI) is a formula that the gunite pool industry adopted to determine water balance and predict whether water will form calcium scale or dissolve it. Some pool industry professionals insist you should focus strictly on LSI balance, but for fiberglass, that advice can damage your pool. However, an LSI calculator can be helpful for fiberglass pool owners as a secondary tool in keeping critical factors of water chemistry within fiberglass-safe target ranges. 

What Are Fiberglass-Safe Water Chemistry Target Ranges?

  • pH: 7.2 to 7.4
  • Total Alkalinity (TA): 80 to 120 ppm
  • Free Chlorine (FC): 1 to 3 ppm 
  • Cyanuric Acid (CYA): 30 to 50 ppm
  • Calcium Hardness (CH): Less than 120 ppm (NEVERt add calcium)
  • Total Dissolved Solids (TDS): Less than 1,500 ppm (or up to 1,000 ppm above your salt level)

Always use a stain and scale control or chelating and sequestering agent as part of routine care and for winterization. Never use calcium hypochlorite or any calcium-adding products in fiberglass pools. When pH, calcium, and chlorine are all elevated at the same time, the risk of damage to the fiberglass pool gelcoat increases significantly. If only one or two are high, the risk of damage is lower but still present.

What is LSI?

The Langelier Saturation Index was developed in the 1930s by Dr. Wilfred Langelier to help cities predict whether water would deposit calcium carbonate scale inside pipes or dissolve it. The concept later made its way into the pool industry because it’s an easy way to check water chemistry with respect to calcium carbonate.

 

Simply put, LSI looks at pH, alkalinity, temperature, and calcium levels together and estimates whether water is likely to scale (represented with a positive-number LSI) or dissolve calcium (negative LSI).

 

Why is LSI Secondary for Fiberglass Pools?

Concrete and plaster pools contain calcium in their walls. If the water is too “hungry” (what pool pros call “aggressive water”), it pulls calcium out of those surfaces, causing rough spots or etching.

 

Fiberglass pools are different. The shell doesn’t contain calcium, so aggressive water won’t leach anything from it. Instead, the bigger risk is the opposite: too much calcium in the water. When high calcium combines with high pH or high chlorine, it can cause discoloration on the gelcoat. That’s why adding calcium to “fix” LSI—something that works for concrete—can actually damage fiberglass.

How Do I Use LSI in a Fiberglass-Safe Way? Practical Steps to Take

Think of LSI as a final check after you’ve set your fiberglass targets.

  1. Dial in the targets first: pH between 7.2 and 7.4, TA between 80 and 120 ppm, FC at 1 to 3 ppm, CYA at 30 to 50 ppm, and CH less than 120 ppm.
  2. Check LSI last: Aim for roughly -0.30 to +0.30.
    • In cold water, from late fall through winter, a slightly negative LSI is acceptable.
    • Do not push water chemistry factors outside of fiberglass-safe ranges in order to hit perfectly balanced 0.0.
  1. If LSI is too positive and water is scale-prone:
    • Bring pH toward 7.2 to 7.4 without overshooting high.
    • Confirm TA is within 80 to 120 ppm.
    • Do not add calcium. Keep using your stain and scale control.
  1. If LSI is too negative and water is aggressive:
    • Make sure pH is not below 7.2 and adjust gently.
    • Bring TA within 80 to 120 ppm.
    • A cold-weather LSI total slightly below -0.30 can be acceptable for fiberglass.

Looking for more information on water chemistry and fiberglass pool maintenance? Explore Thursday Pools’ Ultimate Fiberglass Pool Maintenance Guide.

 

And if you’re ready for personalized advice or want to talk about water chemistry ranges with a local pool pro, connect with an independent Thursday Pools dealer near you.

 

Frequently Asked Questions About LSI

My LSI is +0.5 but my pH is 7.6. Should I add calcium to bring it down?

No. For fiberglass, keep calcium hardness levels less than 120 ppm. Lower pH toward 7.2 to 7.4 and verify total alkalinity between 80 and 120. Keep using a stain and scale control product. Calcium may fix LSI for concrete pools, but it causes more harm than good in fiberglass.

What if my fill water is hard?

Use a stain and scale control product and manage pH and total alkalinity. The goal is to prevent calcium fallout onto the gelcoat, not raise calcium. 

Can I “balance for LSI” during winter?

You can allow a slightly negative LSI in cold water, but always stay within fiberglass-safe pH and total alkalinity ranges, keep calcium hardness less than 120 ppm, and use additional stain and scale control at pool closing.

Do I need to calculate LSI every time I test my pool water?

No. Focus first on fiberglass-safe water chemistry ranges for pH, alkalinity, chlorine, and calcium. 

Why is calcium hardness so important for fiberglass pools?

Fiberglass shells don’t need calcium for structural protection, unlike concrete pools. Too much calcium in fiberglass pools leads to scale, discoloration, and rough surfaces, so always keep levels less than 120 ppm. If you have hard source water and your calcium is high, be sure to use a stain and scale control product.

What Can Damage a Fiberglass Pool?

 

It’s easy to get caught up in the excitement of something new. Whether it’s a car, a boat, or an inground swimming pool, it’s only natural to want to do as much research as possible before signing on the dotted line. You’ll want to know how long it’ll last, right? If you’re currently considering an inground fiberglass pool and trying to cover all your bases, you may have searched for potential problems such as, “What can damage a fiberglass pool?” and “Can you scratch a fiberglass pool?” Perhaps you’ve also looked up fiberglass pool gelcoat problems and fiberglass pool bulging walls. This post covers a few common concerns you may have heard regarding fiberglass pools, how they happen, and if you can prevent them or repair them if they occur.

How Does Fiberglass Pool Chemistry relate to these issues?

A big part of the longevity of your fiberglass pool is the water chemistry. Water chemistry can be tricky for any pool owner, and it’s best left to the professionals that do pool maintenance for a living. However, as a fiberglass pool owner, it’s important to understand water chemistry guidelines so you can take the best preventative care possible of your pool shell. You might have heard someone ask, “why is my fiberglass pool turning white?” It is often because of an imbalance in the water chemistry. A fiberglass pool surface finish is very durable but it is not indestructible. Water balance is vital to ensuring protection for the surface finish of your fiberglass pool.

Remember that even when using a professional to manage your fiberglass pool’s water balance, you will want to take responsibility and know the parameters  of keeping your water balanced. Balanced pool water is neutral, meaning that the water is neither corrosive nor scaling. Bear with us – we’re going to get into a bit of science here.

 A commonly used measure for water balance is the Langelier Saturation Index (LSI). The LSI is a model developed to estimate the diversified state of water by W.F. Langelier, a professor at the University of California in Berkeley. Paraphrasing The Journal of Water Resource and Protection, Vol. 9, No. 2, February 6, 2017, the LSI can be used to control corrosive waters incorporating parameters including acidity, alkalinity, pH, and calcium ions. The proper LSI level is 0.

High calcium levels can contribute to rising pH, leading to white deposits and surface discoloration on your fiberglass pool. When both calcium and pH are elevated, the result is often irreversible damage to the gelcoat finish. The good news? It’s also 100% preventable with proper water care. Often, the manufacturer of your pool shell provides you with an owner’s manual that gives water level recommendations, so we suggest following those. Keep in mind that our recommendations are specifically for fiberglass pool shells. Our owner’s manual recommends your calcium levels remain remain below 120 parts per million. Source water can often run above 120 parts per million. In that case, it is imperative that you regularly use a stain/metal and scale control product. One that chelates the calcium and shields it from discoloring your pool finish. These are two stain/metal and scale control products that we tested and work well: Pool Stain Remover’s Scale and Stain Eliminator and Orenda’s SC-1000. Make them part of your pool care routine from the start. 

We recommend the chlorine residual in your pool, which is the chlorine leftover once disinfection and oxidation has occurred, should be maintained at one to three parts per million and never exceed five parts per million as this can damage the pool surface.

Per our recommendations, the pH level, which measures the acidity or basicity of water, should be maintained between 7.2 and 7.4.

The total alkalinity measures the amount of bicarbonate material in pool water and indicates the water’s capacity to withstand changes in pH. We recommend it be 80 to 120 parts per million.

Finally, cyanuric acid prevents the decomposition of free chlorine in the pool water. As a stabilizer for chlorine, we recommend your cyanuric acid levels be at 20 to 50 parts per million. As levels rise above 100 parts per million, chlorine is not as effective at killing bacteria and algae. 

Thanks for sticking with the science there. It’s helpful to understand it to ensure the person maintaining your water balance is doing it correctly. You may also want to familiarize yourself with water test kits and educational booklets such as “Pool & Spa Water Chemistry” and “I Never Liked Chemistry.” 

Other surface issues, like spider cracks in fiberglass pools, are generally surface-level concerns and don’t impact the pool’s structure. These cracks can occur when a large amount of pressure is applied to an area or manufacturing processes render the gelcoat too thick. Scratches can occur on the surface, as well. However, gelcoat in fiberglass pools tends to be tough (but smooth) and resistant to scratches, whether they be from you or your dog’s paws, so hopefully you won’t run into this yourself. 

As previously mentioned, some issues can occur primarily due to improper manufacturing practices, such as osmotic blistering. These tiny bubbles appear on a pool’s surface when water molecules pass through the pool’s gelcoat and meet with the polyester resin layered inside. Though they don’t look very appealing, they also don’t impact the pool’s structure and are purely a cosmetic concern.

Can Issues With Fiberglass Pools Be Fixed or Prevented?

Discoloration/Residue: Regular water testing, maintaining proper water chemistry, and certain equipment add-ons can prevent discoloration and deposits on a fiberglass pool’s surface by suspending calcium and reducing the need for high levels of chlorine. Obtaining guidance from a professional is the best way to address these issues, but the homeowner can often perform the correction methods.

Spider Cracks: Fiberglass pool gelcoat repair methods are available to restore the gelcoat after cracking. Your independent pool builder or maintenance company will likely be able to point you in the right direction for who can provide these services.

Pool Wall Bulging: When it comes to fiberglass pool walls bulging: yes, it can happen. But generally, it is due to the pool’s structure or incorrect installation practices. When not properly installed or not durable enough in structure, a fiberglass pool’s walls can bulge due to groundwater pressure combined with the earth’s natural tendency to shift. The best way to prevent this issue is to make sure you go with a manufacturer that accounts for both flexibility and rigidity in their pools’ structures. Some innovations, like the Thursday Pools Geo-Anchoring Pool wall®, provide additional structural support by anchoring the pool to the earth to help prevent bulging or shifting if water must be lowered according to the TP owners manual.

Conclusion

We always applaud those who do their research before splashing into the world of fiberglass pools. We hope this has not only given you a better understanding of what can damage a fiberglass pool, but also made you feel more comfortable moving forward in the pool ownership process. 

If you’d like to get in touch with an independent dealer in your area, click here. Don’t feel quite prepared to take that next step? We encourage you to try out our pool cost calculator for ballpark estimates or our Idea Book for backyard inspiration.

 

 

 

The Best Robotic Cleaners For Inground Fiberglass Pools

Every fiberglass pool owner should have a thorough and working knowledge of necessary pool maintenance. It’s essential to stay on top of care and maintenance from the time you open your pool in the spring through closing it for the winter. Robotic pool cleaners can be a great help when it comes to keeping dirt and debris out of your pool, saving you time and effort. With an overwhelming amount of options available on the market, all with various features and benefits you may or may not need, deciding on a robotic pool cleaner can feel overwhelming. In our experience, the following four models are great at getting the job done while you sit back and relax.

 

Hayward TigerShark

 

A Hayward TigerShark robot can clean a 20’ x 40’ pool’s floors, walls, and waterline in just three hours. There are three configurations to choose from, including the standard TigerShark, the TigerShark Plus with remote control capabilities, and the TigerShark QC featuring a patented 90-minute quick-cleaning alternative mode. All the TigerShark models have an easy-to-clean cartridge filter system and a 24-volt motor to conserve energy and save you pool maintenance costs over time.

 

Thursday Pools TigersharkAverage Price: Less than $1,500

 

Highlights:

  • Easy-to-clean cartridge
  • Lightweight design
  • On-board pump for intense vacuum power
  • Pool length: Up to 40 feet
  • 1- to 3-year warranty depending on model
  • Cordless
  • Programmable

 

Dolphin Nautilus CC Plus with Wi-Fi

 

Dolphin’s Nautilus CC Plus with Wi-Fi features an award-winning design backed by more than 25 years of technology innovations. The unit weighs less than 21 pounds and includes a 2.5-year warranty. A swivel system enables tangle-free operation, and a smart navigation system allows the vacuum to clean a pool in approximately two hours. The Nautilus CC Plus features rubber tracks that grip the pool surface in order to get into tight corners, up walls, and across tanning ledges. A fine filter traps algae, dirt, bacteria, and biofilm, while a high-RPM system provides a deep clean.

 

With Wi-Fi connectivity, you can run the Nautilus CC Plus from anywhere with just a few taps on the cleaner’s smartphone app.

 

Thursday Pools' dolphin robotic cleaner for inground fiberglas pools.Average Price: Less than $900

 

Highlights:

  • East-to-clean cartridge
  • Lightweight design
  • Pool Length: Up to 33 feet
  • 2.5-year warranty
  • Swivel cables for tangle-free operation
  • Programmable

 

Polaris 9450 Sport

 

The Polaris 9450 Sport is a lightweight robotic cleaner that can clean your pool in less than two hours. The “Aqua Trax” tires enable the Polaris to move freely across floors, steps, and walls. It has a navigation system that automatically controls the robot’s position, providing cleaning coverage without hang-ups. The 9450 Sport uses Polaris’s Vortex Vacuum technology that filters out particles and quickly gathers large debris. With a seven-day programmable timer, you can customize your settings and select the cleaning modes that work best for you. After cleaning, the 4950 Sport surfaces at the touch of a button, waits for you to grab it, then automatically evacuates water for effortless removal from the pool.

 

Thursday Pools' polaris robotic cleaners for inground fiberglass pools.Average Price: Less than $1,000

 

Highlights:

  • Easy-to-access filter canister
  • Lightweight design 
  • Easy to remove from the pool
  • 2-year warranty
  • Programmable

 

Aquabot X4 

 

The Aquabot X4 is ideal for all pool shapes and sizes with its 4WD non-marring, high-grip wheels for superior traction. The X4’s ultra-fine mesh filter baskets capture dirt, debris, and fine particulate down to 2 microns in size. The Anti-Tangle Swivel prevents the rover from getting hung up, and the straightforward interface makes it easy to operate and program. You can choose cleaning cycles between one and two hours long while programming for it to run automatically every 48, 72, or 96 hours.

 

Thursday Pools' robotic cleaner for inground fiberglass pools called the aquabot.Average Price: Less than $800

 

Highlights:

  • Easy-to-access filter
  • Lightweight design
  • Pool Length: Up to 60 feet
  • Energy-efficient
  • 3-year warranty
  • Programmable

 

Looking for more information on fiberglass pool care? Explore Thursday Pools’ Ultimate Fiberglass Pool Maintenance Guide for a thorough look at everything you need to know.

 

And if you’re ready for personalized advice, connect with a local independent Thursday Pools dealer near you.

 

Frequently Asked Questions About Robotic Pool Cleaners

 

Do robotic pool cleaners work with fiberglass pools?

Yes. Robotic pool cleaners work great with fiberglass pools because they use gentle brushes and smart navigation systems that scrub floors, walls, and waterlines without scratching the gelcoat. They lift algae, dirt, and debris while saving you time compared to manual cleaning.

 

How much do robotic pool cleaners cost?

Most high-quality robotic pool cleaners cost between $800 and $2,000. Prices vary based on features such as Wi-Fi connectivity, programmable timers, and quick-clean modes. While the upfront cost may feel significant, a robotic pool cleaner saves you money long-term by reducing chemical use, conserving energy, and extending the life of your pool equipment.

 

Do I still need other cleaning tools if I have a robotic pool cleaner?

Yes. Robotic cleaners handle most of the heavy lifting, but you still need a pool brush, skimming net, and manual vacuum for quick cleanups or after storms. These tools complement your robotic cleaner and make sure every corner of your fiberglass pool stays spotless.

 

How long does it take a robotic pool cleaner to clean a pool?

Cleaning time depends on the model and pool size. Many robotic cleaners can clean an average 20’ x 40’ fiberglass pool in two to three hours. Some models even feature quick-clean settings that finish in as little as 90 minutes.