What Can Damage a Fiberglass Pool?

Posted on October 6, 2023May 28, 2025 by megwalker

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.

Fiberglass Inground Pool Shapes

Everything You Need To Know About Beach Entry (Or Zero Entry) Fiberglass Pools

Standard Warranty Registration and Acknowledgement Agreement

Thursday Pools would like to thank you for choosing a Thursday fiberglass swimming pool. We are honored to be a small part of the memories you will have in and around your new fiberglass pool for many years to come.

Please follow these next steps to complete your warranty registration.

1) Read Acknowledgement and Agreement

2) Read Warranty and Safety Documentation

3) Submit the Form

1) Read Acknowledgement and Agreement

To ensure you understand the relationship between the manufacturer and the installer and the proper care and safe use of your new pool, please take a few minutes to review the information carefully and complete the form below. Completing the form below will ensure your order is processed by the dealer without any delay and allow for an efficient response to any warranty issues you may have in the future. Your pool shell warranty will not begin until the day the pool is installed.

ACKNOWLEDGEMENT AND AGREEMENT OF THE LIMITED ROLE OF
THURSDAY POOLS, LLC AND RIVER POOLS FRANCHISING, LLC

The dealer’s customer listed below acknowledges and agrees as follows:
Thursday Pools, LLC (“Thursday”) manufactures pool shells for the brands Thursday Pools® and
River Pools® and sells those pool shells to independently owned and operated franchisees and dealers
(collectively referred to herein as “Installers”). Thursday does not install pool shells and is not involved in
Installers’ pool installations.

River Pools Franchising, LLC (“Franchising”) provides independently owned and operated
River Pools franchisees with the right to market the River Pools brand of pool shells as a franchisee.
Franchising does not manufacture pool shells. Franchising does not install pools shells and is not involved
in Installer pool installations.

Installers enter into contracts with customers to install pool shells, and Installers purchase pool
shells from Thursday. Neither Thursday nor Franchising is a party to the Installer’s contract with the
customer, and Installers are not agents of either Thursday or Franchising for any purpose. Customer
acknowledges that it is contracting only with Installers and, other than the warranty on the pool shell, its
sole recourse is against Installers. Customer further acknowledges and agrees that Installer is not an agent,
express or implied, of either Thursday or Franchising and Installer has no authority to act on behalf of
Thursday or Franchising. Thursday is only a supplier of a pool shell to the Installers. Neither Thursday
nor Franchising is a guarantor of Installer’s performance or an endorser of Installer’s services, and neither
Thursday or Franchising is responsible for Installer’s installation or other contract performance.

Installers place orders for pool shells with Thursday, and Thursday makes the pool shells
available for pickup by Installer’s carrier at the time prescribed by Thursday and upon full payment by
Installer for the pool shell. Installers then make arrangements for transporting the pool shell. Customer
acknowledges that Thursday’s obligations to customer are limited to the warranty on the pool shell, and
customer further acknowledges that Franchising has no obligations to customer.

Customer’s acknowledgement and acceptance of these terms are a condition precedent to
customer’s contract with Installers to install a Thursday Pools or River Pools branded pool shell, and to
Thursday’s obligation to sell a pool shell to Installers. These terms are not and may not be changed by any
written or verbal statements or marketing materials and may be changed only by a writing signed by the
chief executive officer of Thursday and Franchising.

Customer acknowledges that customer has read and understands these terms and conditions; and
that customer has consulted, or been provided an opportunity to consult, with legal counsel of customer’s
choosing before signing below. If customer has any questions regarding the foregoing, please contact
Thursday at 877-929-7665 ext. 0, or sales@thursdaypools.com.

2) Read the Warranty and Safety Documentation

Below are important documents regarding the care and use of your new fiberglass swimming pool. Please download them and keep them for your records.

*Upon completion of this registration, you will receive an email with all of these documents.

3) Submit the Form

Small Fiberglass Pools

Choose Your Pool Color

How Long Does a Fiberglass Pool Last?

What are My Rectangle Fiberglass Pool Shell Options?

Posted on April 18, 2022June 16, 2025 by krista

Commonly, pool buyers ask, “what shapes do fiberglass pools come in?” While the simple answer is that fiberglass pool designs are primarily either rectangular or freeform, you may be surprised by the remarkable variability of fiberglass pool shell options. The sizes, varying depths, and vast assortment of features available in fiberglass pools allow you to tailor your choice depending on your yard size, style, and the activities you want to enjoy in and around your backyard pool. Rectangular-shaped pools have clean, sharp lines and lend to a traditional elegant or modern setting. They maximize the swimming area and perimeter yard space. In this post, we’ll describe our rectangle pool shell options.

Goliath

The Goliath is big on style and functionality. Offering the best of both worlds, Goliath provides plenty of room for entertaining and swimming.

A wide-open swim lane down the pool’s center is conducive to lap swimming or floating with friends.
Bench seating flanks the steps for ample room to relax and socialize.
Two sets of curved entry steps in the shallow end and swim-out ledges in the deep end provide easy entry and exit areas or another option for sitting.

Monolith

Monolith is the only Type One diving pool design in Thursday Pools’ collection and is suited for pool owners looking to take a plunge, float and relax.

The 40’-long pool has an 8′ 6″ deep end and a large, flat-bottomed shallow end perfect for playing pool games.
The angled steps make it easy and safe to enter and exit the pool.
The shallow-end bench makes an excellent spot for relaxing and socializing.
The dual deep-end benches make it a little easier for those deep-end lovers to enter and exit the pool or sit and rest.

(Note: *Thursday Pools strongly recommends that diving boards and slides not be installed or used with its pools, given the inherent dangers associated with diving boards and slides in residential pools. These dangers include brain, spinal cord and other severe permanent injuries, and death. For that reason, Thursday Pools does not manufacture or sell diving boards or slides. If, despite this warning and recommendation, the owner decides to install or use a diving board or slide, the owner assumes all risks inherent with a diving board or slide, and Thursday Pools further warns that diving boards and slides require minimum depths and distances and must be installed and used in strict compliance with the equipment manufacturer‘s specifications and ANSI/NSPI, ANSI/APSP, and ANSI/APSP/ICC standards, as well as in compliance with all applicable laws, rules and regulations. The owner is responsible for making sure the pool is appropriate for diving boards and slides and otherwise meets all standards and laws for diving pools, and the owner must consult the diving board or slide manufacturer and/or installer as to the appropriateness of the pool for the diving board or slide and that its installation, location and use meet all standards and laws for diving and slide pools.)

Aspen

The Aspen is a best-seller with five different available sizes to fit almost any yard. Sunbathers and swimmers alike rate this pool a favorite.

A large, luxurious 12-inch deep tanning ledge can comfortably accommodate two lounger chairs while leaving plenty of room to enter and exit the pool.
A wide-open swim space is ideal for swimming laps.
Curved steps stretch across the width of the pool and offer easy entry and exit.
An extended bench makes for a nice spot to enjoy a beverage or engage in great conversation.
Deep-end swim-outs are perfect for relaxing in the sun or watching other swimmers do their thing.

Grace Beach Entry

Thursday Pools’ beach entries (Patent US 10,472,839) are zero-entry fiberglass pools with a gently sloping entry into the water. Grace creates a resort feeling and is a stunning social centerpiece for entertaining.

A gently sloping beach entry makes it easier for people of all ages and their pets to enter and exit the pool. The area also makes a great spot for sunbathing and can accommodate two lounger chairs.
A wading area is perfect for cooling off shallow waters and can double as a play area for small children.
The extended bench provides a place to relax and enjoy a conversation.
Dual deep-end swim-outs can be used for exiting the pool or just chilling out.
Even with all the places to relax and socialize, Grace still has a wide-open swim area for those wanting to exercise.

Lil Bob

Lil Bob is perfect for games and the swimmers who are content to watch the action from the wet sideline. A standing depth, flat bottom design with two 12-foot-long benches helps Lil Bob keep things sporty and social.

Full-width ergonomic steps make it easier for everyone to enter and exit the pool.
A standing-depth, flat bottom design makes Lil Bob the ideal pool for water games and activities. It’s regulation size for water volleyball.
Each of the 12 foot long and 18 inches deep, two facing benches make excellent court-side seats and a conversation area.
Lil Bob includes an open swim area thanks to strategically placed benches and steps.

Lil Bob LX

Lil Bob LX is an extended version of Lil Bob, designed to include a tanning ledge and wading area with integrated bench seating. Everyone can find a favorite spot in Lil Bob LX.

A large tanning ledge easily accommodates two lounger chairs while leaving room for entry and exit.
Just past the tanning ledge, a wading area provides ample space to entertain your littlest ones while the big kids get a workout in the game-ready, open swim area.
Generous wraparound benches allow family and friends to enjoy hours of relaxed conversation.

Spirit

Spirit appeals to social butterflies, swimmers of all ages, and water activity lovers.

With its court-sized flat-bottom design, Spirit allows pool-goers to get their game on.
Extended bench seating and full-length steps at both ends of Spirit invite swimmers to rest and socialize.
At 4’6″ deep, swimming is comfortable for a variety of ages.

Sea Turtle

While it is a smaller pool, Sea Turtle is still big fun. Perfect for smaller yards, Sea Turtle gives you swim and play space and can accommodate therapy jets.

It is medium depth throughout for standing and chatting or even a little game.
Wraparound benches flank the entry steps, creating an intimate conversation area where your group can relax the day away.

While each of the rectangle fiberglass pool shell options have different features, all pools by Thursday Pools are:

Quicker to Install: Fiberglass pools are manufactured in a controlled environment and then shipped to the site for installation, taking just a few weeks on average during typical pool installation seasons.
Aesthetically Pleasing: The durable gelcoat finish of a Thursday Pool retains its beautiful appearance.
Non-skid: Take a glance at a Thursday Pools fiberglass pool, and you might think it’s slippery. Don’t let the shiny appearance fool you. The surface is non-skid and non-snag – perfect for kids and pets! (Of course, always be careful when entering and exiting any swimming pool.)
Durable: We build fiberglass pools from Thursday Pools to last. The multi-layer composite fiberglass construction and innovative design features make fiberglass very robust.
Feature-laden: The designers at Thursday Pools pay attention! They understand what people want and deliver pool designs that allow homeowners to get peak enjoyment out of their pool.
Lower maintenance: Thursday Pools are resistant to algae and mineral deposits and do not have seams or the porosity of other pool types. That saves you hours of work and many dollars every year. With proper water chemistry, they can last with minimal maintenance or need for acid washing, resurfacing, or re-lining.

Do you think a rectangle fiberglass pool design is right for you but are still unsure of the size and features you want? Our Pool Selector Tool can help you narrow down your choice.

What’s the Cheapest Inground Pool Cost?

Posted on March 21, 2022June 16, 2025 by kristin

If spending more time with loved ones (or by yourself) outdoors is climbing on your “should-have” list, and you have the space for an inground pool, you may have started an online search. Being a conscientious consumer, you could have landed here searching for the cheapest inground pool or even the “cheapest inground pool near me.” While no inground pool is “cheap,” this post gives an honest comparison of costs for vinyl liner, gunite, and fiberglass pools. We know an inground pool is a significant investment, so we hope this post will help you make an informed decision about inground pool costs.

Vinyl Liner Inground Pool Costs

Vinyl liner pools are generally the cheapest inground pool type with regard to upfront costs; however, their costs can increase significantly based on several factors. A ballpark figure on the average price of an inground vinyl liner pool is around $25,000 to $65000. Some constraints with vinyl you’ll want to be aware of:

Unique freeform shapes can add to your upfront price, as well as vinyl replacement costs, as manufacturing a custom liner adds time and materials.
High-end features such as bench seating or wraparound steps can add to your cost and may lead to further maintenance needs due to vinyl’s tendency to attract algae and become slippery.
The lifetime ownership, including the annual maintenance cost will offset some initial cost savings.
As previously mentioned, vinyl liner pools can attract algae, so you must clean them more often to keep them at bay. Expect to spend (or pay someone to spend) around four to eight hours per week on vinyl liner pool maintenance.
You could estimate maintenance expenses around $11,000 to $17,000 over ten years, excluding liner replacement costs.
Vinyl liners usually need to be replaced about every seven years (or fewer if the pool hasn’t been properly maintained), costing about $3,000- $7,500 on average.

Gunite Inground Pool Costs

Gunite pools typically cost the most to install, and their prices are the most varied across the country, depending on your location. In some regions, they are the high-volume choice of installers, and installation costs can be competitive. You tend to see more gunite installations in sunbelt states that are not subject to the freeze/thaw cycle. The national average price of a gunite pool is between $50,000 and $120,000. Here are some of the cost factors for gunite:

Freeforms generally cost more than basic shapes, and depending on how complicated the design is, the complexity may add more cost to the bottom line.
Each build is custom. Gunite costs more as you add features and options.
The porosity of gunite attracts algae and mineral deposits. It requires significant time and money to keep it clean. Expect to spend (or pay someone to spend) around four to eight hours per week on gunite pool maintenance.
Gunite pools usually require an acid wash to remove algae and mold every three to five years, and due to multiple acid washes, they often require replastering about every ten years.
Based on the average costs of regular pool maintenance tasks and requirements (such as acid washing, general cleaning, replastering, electrical/chemical usage, etc.), concrete pool owners can expect to pay $27,000 to $40,000 over 10 years for maintenance.

Fiberglass Inground Pool Costs

Fiberglass pools will usually fall in the middle between vinyl and gunite on the initial installation cost. However, lifetime ownership and annual maintenance costs tend to be lower than vinyl and gunite. HomeGuide’s 2024 inground pool cost guide reports that the average fiberglass pool price is between $30,000 and $85,000. However, many pool builders in our network report that their customers choose packages closer to $70,000 and $135,000. Some considerations of fiberglass pools relative to cost include:

Regardless of shape, the pricing is relatively consistent at around $1,800 per linear foot, except for beach entry fiberglass pool designs which tend to cost about 15 percent more.
Built-in features such as wraparound steps and benches, tanning ledges, and swim-outs do not cost extra, but they must already be part of the design, as fiberglass pools are built from pre-existing molds.
Easy access is essential to keeping costs down because they are delivered in one piece and not built on-site.
They are resistant to algae and require the lowest maintenance compared to the other inground pool types, needing only about an hour or two per week, and their ten-year cost for maintenance is around $5,000-$15,000.

Factors Affecting Any Inground Pool Cost

Some factors drive up costs, no matter what pool type you choose.

What’s the cheapest inground pool shape? Pool size affects the price of fiberglass pools rather than shape. However, for gunite and vinyl liner pools, the more complex the shape, the higher the cost.
What’s the cheapest pool size? Generally speaking, small inground pool costs tend to be less than larger ones for installation and maintenance.
Site conditions factor into pricing. Clay, sand, rock, and groundwater can all pose problems when installing any pool. Average excavation costs range from $2.50 to $15.00 per cubic yard for easier soil conditions, but more challenging conditions can cost $50 to over $200 per cubic yard.
Insurance companies and states or local agencies may require pool fencing. Fencing costs average around $15 to $25 per linear foot.
Pool cover prices vary. An automatic pool cover costs $8,000 to $20,000 installed and $1,000 to $3,600 for a manual cover.
Extra features add to the price. Additional features such as heaters, bubblers, deck jets, cascades, LED lighting, slides, and diving boards will also add to the cost.

Cheapest Fiberglass Pool Designs

At the end of the day, we are a fiberglass inground pool manufacturer and that is what we know best. So if you decide to look at lifetime costs, want to stay on the cheaper side, and want to check out some less expensive small fiberglass pool designs, one of the following may be the pool for your lifestyle:

Aspen. The smallest available size is 12’ x 25’ with a depth of 5’1”. The Aspen features a wide tanning ledge, full-length steps, and an extended bench. And it has a wide-open swim area and courtesy ledge throughout the deep end.

Goliath. Like Aspen, this pool comes in multiple sizes, the smallest being 12’ x 25’ with a depth of 5’4”. The Goliath offers a surplus of swim space, along with dual-corner entry steps, and shallow and deep end benches.

Sea Turtle. This pool comes in one size: 9.5’ x 19.5’. Sea Turtle is a flat-bottom pool with a depth of 4’6”, which is ideal for socializing and water activities. Walk-in steps and long benches make it family and pet-friendly, and it’s perfect for entertaining guests.

Pearl. Measuring 15’ x 25’ with a 3’9” depth, the Pearl is a shell-shaped pool that is unique. It’s great for socializing and sunning, with room for two ledge loungers and wrap-around benches.

More Tools for Inground Pool Estimating

If you’re looking for ways to get ballpark prices for pool installation, there are inground pool cost estimator tools out there. Get an estimate on your dream fiberglass pool project with our Pool Cost Calculator. If you are not sure which design is right for you, try our Pool Selector Tool to help you narrow it down. Finally, your best tool for the most accurate estimate and advice is a pool builder. Get connected to a pool builder near you and become one step closer to some of the best memories of your life.

Everything You Need to Know About Inground Pools: Comparing Fiberglass, Vinyl, and Gunite Options

Whether you’re making a mad dash to the end or first dipping your toe into the wading-area waters of inground pool ownership, this guide includes everything you need to know to compare the three inground pool types. From installation processes and long-term maintenance needs to overall costs and exciting design possibilities, you’re in the right place to begin your inground pool conversation and compare fiberglass, vinyl liner, and gunite (concrete) pools.