Fiberglass Pool Maintenance Guide: Schedule, Chemistry, and Costs

Fiberglass Pool Maintenance Schedule: Weekly, Monthly, and Seasonal Tasks

What Tools Do You Need to Maintain a Fiberglass Pool?

Skimmer Basket

The skimmer is the opening on the pool wall near the water’s surface. Water circulates toward it, drawing in floating debris before it sinks. Check and clear the basket as part of the weekly routine.

Pump Strainer Pot

Located at the front of the pump, the strainer pot catches debris before it reaches the filtration system. A clogged strainer puts extra strain on the pump motor and slows water circulation. Clear it consistently.

Pool Filter

The filter removes fine particles that pass through the skimmer and strainer, including sunscreen residue, sediment, and other material that clouds water or reduces sanitation. Depending on usage level and water quality, cartridge filters should be rinsed regularly with a hose and inspected each season to determine whether replacement is needed.

Soft Nylon Pool Brush

Use a soft nylon brush on the walls and floor of the shell. Nylon bristles clean the gel coat effectively without scratching it. Wire brushes and steel wool are not appropriate for fiberglass. Learn more about brushing frequency and best practices in our blog post, Do You Need to Brush a Fiberglass Pool?

Microfiber Cloth

Use a soft microfiber cloth to wipe the waterline where body oils, sunscreen, lotions, and other residue can collect. Regularly wiping this area helps prevent buildup and keeps the gel coat looking clean without using abrasive pads or harsh scrubbing tools. 

Skimmer Net

A mesh net on a telescoping pole handles manual surface debris removal between filtration cycles. It works well for leaves, grass clippings, insects, and flower petals.

Pool Vacuum Head and Hose

For debris that settles on the floor and walls, a manual vacuum on a telescoping pole connects to the pool’s suction line and draws material into the filtration system.

Robotic Pool Cleaner

Robotic cleaners operate independently of the pool’s pump and filter, covering the floor and walls without drawing on the main filtration circuit. They reduce manual vacuuming time significantly and suit fiberglass surfaces well. Learn more in our guide, The Best Robotic Cleaners for Inground Fiberglass Pools.

How Do You Protect a Fiberglass Pool's Gel Coat

The gel coat finish is the smooth outer layer of the fiberglass shell. It gives the pool its color and surface feel, and it functions as the primary barrier against water intrusion, algae, and chemical damage. Protecting it comes down to three things: using the right cleaning tools, keeping water chemistry within the recommended ranges, and avoiding contact with sharp or abrasive materials.

Water chemistry is the most consequential factor in gel coat protection. Cleaning tools remove surface buildup, but chemical damage from improper water maintenance cannot be reversed with a brush. 

What Are the Correct Water Chemistry Levels for a Fiberglass Pool?

The ranges and recommendations below reflect Thursday Pools’ manufacturer guidance for fiberglass pools.

Test water at least weekly during the swimming season. Monthly digital testing through a pool professional gives a more precise picture and catches chemistry drift that home test kits can miss. Before hiring a pool professional for ongoing service, confirm that they are familiar with fiberglass-specific chemistry ranges. Local professionals experienced primarily with concrete pools sometimes apply recommendations that do not suit a fiberglass surface.

What Are the Most Common Fiberglass Pool Problems?

How Much Does Fiberglass Pool Maintenance Cost?

Annual maintenance costs depend on pool size, local climate, source water chemistry, how much of the work you handle personally, and what equipment the pool uses. 

For context: concrete pools require resurfacing every 10-15 years at $6,000-$15,000 or more, according to HomeGuide, and carry higher annual chemical costs due to the porous surface. Vinyl liner pools require a new liner every 5-15 years, typically costing $3,000-$7,500, according to HomeGuide. Fiberglass pools carry no equivalent recurring expense, which contributes to lower total maintenance costs over the life of the pool.

DIY maintenance covers the cost of testing supplies and water chemicals, cleaning tools and replacement parts, filter cartridge replacement, and the electricity to run the pump and equipment. In our experience, most owners typically spend roughly $500 to $1,500 per year. Pools in regions with hard water or high-use seasons often fall at or beyond the higher end of that range.

Professional maintenance adds labor to the supply costs above. Monthly service visits typically run $100-$300 depending on region and scope. Annual full-service contracts vary significantly by area. Based on our experience with local pool builders and maintenance professionals, budgeting $1,000-$3,000 per year for professional upkeep, in addition to chemical costs, is a reasonable starting point.

Should You Maintain a Fiberglass Pool Yourself or Hire a Professional?

When hiring a pool professional for ongoing service, confirm that they have fiberglass pool experience. Some professionals apply water chemistry protocols developed for concrete pools that are not appropriate for fiberglass. For example, the recommended calcium hardness range for a Thursday Pools fiberglass pool is less than 120 ppm, which is significantly different from standard concrete pool recommendations. Applying the wrong targets leads to the surface problems described in the troubleshooting section above.

How Do You Open, Maintain, and Close a Fiberglass Pool?

Opening Your Fiberglass Pool

The basics of a successful pool opening include:

1. Remove, clean and store the pool cover.
2. Reinstall any equipment removed for winter storage.
3. Restore water to normal operating level if needed.
4. Run the filtration system and allow the water to circulate for at least 24 hours.
5. Test and adjust all chemistry parameters before the first swim of the season.

The right time to open your pool will depend largely on where you live, but a good rule of thumb is to wait until daily temperatures are consistently above 70 degrees. If you wait too long to open your pool, higher temperatures could encourage the growth of algae and bacteria, so it’s best to get ahead of that process.

Many homeowners view Memorial Day weekend as the unofficial opening of the swimming season. If you plan to hire a professional service for opening or need new equipment, scheduling by early April avoids the backlog that typically builds through May and into Memorial Day weekend.

In-Season Fiberglass Pool Maintenance

Continue to check, adjust, re-check, and adjust again to ensure your pool’s water chemistry stays within recommended ranges throughout the swimming season. Weekly home testing and recording is recommended, while monthly digital testing at your local pool professional’s facility can give you an even clearer picture and detailed breakdown of what’s in your water. 

Pool Filter Maintenance

Your pool’s filter performs critical functions during the swimming season, such as removing organic particles and debris that could leave water looking cloudy or unsanitary and unpleasant.

There are three main types of filters. Each type operates differently but essentially serves the same purpose of filtering impurities out from your pool water. Regardless of which filter type your pool uses, regular inspections to check for signs of damage should be a staple of your maintenance routine.

Cartridge Filters

• Rinse the element with a garden hose when pressure rises 8–10 psi above the clean baseline
• Consider using an appropriate cartridge chemical cleaner for severe buildup
• Inspect each season for tears, collapsed pleats, or cracked end caps
• Replace when cleaning no longer restores to normal operating pressure

Diatomaceous (DE) Filters

• Backwash when pressure rises 8–10 psi above baseline, then add fresh DE powder
• Repeat two to four times per season depending on usage
• Perform a full teardown and media cleaning once per season

Sand Filters

• Backwash every two to four weeks or when the pressure gauge reads high
• Replace sand every five to seven years when backwashing no longer restores normal pressure

Pool Filter Maintenance

Your pool’s filter performs critical functions during the swimming season, such as removing organic particles and debris that could leave water looking cloudy or unsanitary and unpleasant.

There are three main types of filters. Each type operates differently but essentially serves the same purpose of filtering impurities out from your pool water. Regardless of which filter type your pool uses, regular inspections to check for signs of damage should be a staple of your maintenance routine.

• Cartridge Filters: Cartridge filters have a removable filter element that needs to be periodically cleaned or replaced. Depending on the usage level and water quality, you should clean the cartridges with a hose regularly and considering them every season.

• Diatomaceous (DE) Filters: DE filters use a fine powder made of diatomaceous earth to capture unwanted particles. Maintenance for this equipment involves periodically backwashing the filter and replenishing the DE powder. Depending on how much you use your pool in a typical year, this may need to be done twice to four times yearly.

• Sand Filters: Backwashing is the primary maintenance task for sand filters. Backwashing involves reversing water flow through the filter to flush out any trapped debris. Regularly perform sand filter backwashing maintenance, typically every few weeks or when the filter’s pressure gauge indicates a high-pressure reading.

Closing Your Fiberglass Pool

For fiberglass pools in traditionally seasonal climates, one of the most critical aspects of maintenance is preparing the pool for the winter offseason. 

If your area’s climate undergoes a freeze-thaw cycle, you should plan to close your pool by early fall. When it comes time to close your swimming pool for the season, taking the necessary steps protects the pool through the offseason and makes the spring opening faster and more predictable.

Do not drain a fiberglass pool for winter storage. Removing the water exposes the shell to hydrostatic pressure from surrounding soil, which can cause the shell to shift or crack.

The basics of a successful pool closing include:

1. Ensure water chemistry levels are within the recommended ranges.
2. Brush, vacuum, and skim the pool thoroughly before covering it.
3. Ensure plumbing lines are properly blown out with compressed air and winterized with pool-safe antifreeze as needed to prevent freeze damage. 
4. Winterize the pump, filter, heater, and any other equipment per manufacturer instructions.
5. Install the safety cover.
6. Check the water level periodically throughout the offseason. Add water if rain or snowmelt drops it below the normal range.

What Are the Best Practices for Fiberglass Pool Maintenance?

Consistent maintenance is the most effective way to extend the service life of a fiberglass pool and prevent surface problems. You can maximize the service life of your fiberglass pool and protect your investment by diligently sticking to some best practices for pool maintenance.

• Maintain your pool’s water level. Your pool water should always be at least halfway to the top of the skimmer window.

• Test and adjust water chemistry regularly. Keeping pH, chlorine, total alkalinity, and calcium hardness within the recommended ranges helps protect the gel coat, reduce the risk of stains or scale, and keep the water safe and comfortable for swimmers.

• Use a routine stain and scale control product as directed by the product label. This is especially important if your source water contains high calcium, metals or if your pool is exposed to conditions that can contribute to staining or mineral buildup.

• Check and clean out the skimmer basket regularly to prevent unnecessary wear on your pool pump.

• Skim and vacuum weekly or as needed, especially after heavy use and if storms blow dirt and debris into the water. Keeping debris out can prevent stains and save your filtration system from extra strenuous work. 

• Recognize when to call a professional. You can manage much of your fiberglass swimming pool’s day-to-day maintenance. But if something needs repairs, hire a professional pool maintenance company to ensure your pool is in top shape.

You can avoid many issues with inground fiberglass swimming pools by staying on top of your pool maintenance. Some of the most common mistakes that many novice or first-time pool owners make include: 

• Using harsh solvents or cleaning tools. The smooth, non-porous gel coat of fiberglass pools requires a gentler touch than other pool types. Highly abrasive cleaning tools or agents can corrode the gel coat and do more harm than good. Avoid abrasive pads, wire brushes, steel wool, eraser-style cleaning pads, or aggressive scrubbing tools that may scratch or damage the surface. 

• Using products that are not fiberglass-safe. Not every pool chemical is appropriate for fiberglass surfaces. Avoid using calcium hypochlorite, also known as cal-hypo, and other calcium-based products. These products can contribute to elevated calcium hardness, scale, discoloration, or other surface concerns. 

• Leaving your pool uncovered. Pool covers reduce debris accumulation, lower chemical demand, and limit UV exposure to the gelcoat during the offseason. If you do not cover your pool for the winter, you’ll face a lot more work and costs when it’s time to reopen in the spring. 

• Not maintaining proper water chemistry. When water chemistry is outside the recommended ranges, many other problems can arise. Bacteria can thrive, and the water can become cloudy or unsafe for swimming. High calcium hardness can contribute to scale and surface discoloration, while elevated alkalinity or pH can make the water harder to manage and may lead to long-term surface issues. 

Frequently Asked Questions About Fiberglass Pool Maintenance