Fiberglass Pool Problems and Solutions: A Tulsa Builder's Guide

We once took a job in Broken Arrow that looked routine. The owner wanted a spa added next to their fiberglass pool and new concrete poured around it.

Then we pulled up the old deck.

Before we did, we noticed that the pool had dropped two inches on one side. The concrete around it was sinking. Another company had built it.

What the crew found under that concrete explains more about fiberglass pool problems than any brochure will.

Most pool builders will not say that fiberglass pools do have problems. Some problems are cosmetic. Some cost thousands. You can prevent almost all of them before the shell touches your yard, which is what this guide is for.

There is also one thing you should never do to a fiberglass pool, even when the water turns green. We will get to that too.

Still deciding whether fiberglass fits your yard? Read our pros-and-cons guide first.

Is the Fiberglass Shell the Problem, or Is It the Install?

Most people think fiberglass pool problems come from cheap fiberglass. Most come from three things around the shell.

• The material behind it.
• The water under it.
• The water inside it.

A fiberglass pool is a one-piece shell made in a factory. Jason puts it plainly. It is built the same way you build a boat. That makes it strong, light, and flexible. A flexible shell needs firm support on every side.

Think of a plastic cup set in a hole. Pack firm material around it, and it holds its shape. Let that material wash away, and it leans.

The shell is rarely the problem. What surrounds it usually is.

Not sure which one you have? Send Jason a photo. One clear picture tells him a lot.

Why Does a Fiberglass Pool Drop or Bow?

A fiberglass pool moves when the material under and behind it moves or disappears. The shell is light and flexible, so it needs firm support on every side. Take that support away, and the shell moves into the empty space.

That movement shows up two ways. The shell drops on the side that lost its support. Or a wall bows, bulging out where the water pushes against nothing, or caving in where wet ground pushes against an empty shell. Either one shifts the coping and cracks the deck.

When Jason's crew dug out the ditch behind the shell, they expected sand. The first builder had used it. There was none. Not a trace. Only a large empty cavity between the pool wall and the dirt.

Over the years, rainwater carried the sand into cracks in the ground. With nothing holding that side up, the shell sank two inches and pulled the deck down with it.

Sand is not the only weak choice. Some builders backfill with the dirt they dug out. Nature packed that soil over a very long time, and no machine packs it that tight again.

Here is how Jason prevents it. He sets every fiberglass shell on 5/8-inch chip stone, then backfills with the same stone, dry compacted. No water jetting.

So why does every builder not do it? Cost. A fiberglass build takes 40 to 70 tons of chip stone, depending on the pool's size and shape. Sand costs far less. Buyers never see that line on a quote.

The honest answer on a pool that has already dropped: Jason's view is that there is no real fix once a pool sits in the ground on failed backfill. On the Broken Arrow job, his crew filled the cavity with chip stone while the deck was open. That stops the damage from getting worse. It does not make the pool new again. This is why the backfill question matters so much before you build.

Watch a Silverado Rock shell go into the ground:

Pro Tip: Ask every builder two questions. What do you set the shell on? What do you backfill with? If the answer is sand or native dirt, keep shopping.

How Does Oklahoma Clay Soil Affect a Fiberglass Pool?

A fiberglass pool tilts when the ground under or around it moves. You will notice the waterline sitting higher on the tile at one end, gaps under the coping, or new cracks in the deck.

In the Tulsa metro, clay soil makes this worse. Clay grabs water and swells, then dries and shrinks. OSU Extension notes that soils with 30 percent or more clay expand and contract a lot as they get wet and dry. Spring rain swells it. August heat shrinks it. That cycle pushes and pulls on anything buried in it.

Soft backfill shifts with the clay. Compacted stone does not hold water against the shell, so the shell stays level and supported.

For a deeper look at how local soil affects every pool type, read our guide to Tulsa clay soil.

Solution: A small, stable tilt is often cosmetic. A tilt that grows month to month is not. Mark the waterline at both ends with painter's tape and check it every few weeks. If the gap keeps growing, have a builder look at the backfill and drainage. Fix the drainage first. Water pooling beside the deck feeds the problem.

Can a Fiberglass Pool Pop Out of the Ground?

Yes. It is rare, but it happens. The cause is groundwater pressure, also called hydrostatic pressure.

A full pool weighs a lot. An empty fiberglass shell is light. Jason calls it burying a boat in your backyard. When heavy rain soaks the ground, water collects under the pool and pushes up. A full pool pushes back with its own weight. An empty one cannot.

And Tulsa gets serious rain. The wettest year on record in Tulsa brought 69.88 inches in 1973. After a wet week in May, the ground under your pool can be soaked for days.

This brings us to the one thing you should never do.

Never drain a fiberglass pool yourself. Not for green water. Not for a stain. Not for anything.

Latham Pool, a major fiberglass pool maker, tells owners to consult their dealer before draining a fiberglass pool. Green water, cloudy water, and most stains can be fixed with the pool full.

Jason builds a safety valve into every fiberglass install. He adds plumbing that lets him pump groundwater away from the pool and relieve the pressure. The chip stone lets that water flow down to the pump point. If your pool ever needs to be drained for a repair, that is how a pro does it safely. The groundwater comes out first.

Solution: Keep the pool full. If it truly needs draining, hire a pro who checks the groundwater first and pumps it down.

Are Cracks in a Fiberglass Pool Serious?

Most cracks in a fiberglass pool are surface cracks in the gelcoat, the smooth colored layer on top. These hairline or spider cracks are cosmetic. A crack that goes through the fiberglass layers underneath is structural. It can leak.

Spider cracks can start anywhere the shell takes stress, such as steps, benches, and corners. A dropped object, a gap under a step, or rough handling during delivery can all start one.

Here is how to tell the two apart.

National repair cost data puts a gelcoat patch for dings, scratches, and cracks at $300 to $400. A full resurfacing runs about $6,500. These are national benchmarks, not Silverado Rock quotes. Your price depends on the pool size and the damage.

One honest note. A fresh patch can look brighter than the sun-faded gelcoat around it.

Solution: Photograph the crack with a coin next to it for scale. Take the same photo a month later. If it has not changed and the water level holds, it is likely cosmetic. If it grows, or the pool loses water, call a pro.

What Causes Blisters in a Fiberglass Pool?

Blisters are small bumps that form when water works into the layers behind the gelcoat. The industry calls this osmosis. Blisters mostly hurt the look of the pool. In severe cases, they spread and weaken the layers.

The resin inside the shell decides how well it resists water. Older and cheaper shells used polyester resin in most layers. Better shells use vinyl ester resin, which resists water much better.

Silverado Rock installs Evo Pools shells. Evo builds every shell with 100 percent vinyl ester resin in all layers. Evo backs each shell with a lifetime structural warranty and a lifetime structural osmosis warranty, plus a 10-year gelcoat warranty. That is the shell maker's warranty, not a whole-pool warranty from any builder.

Solution: You can grind out a few small blisters and patch them. Widespread blistering usually means resurfacing. If you are shopping for a new pool, ask what resin is in every layer. "Vinyl ester in the skin coat only" is not the same as vinyl ester throughout.

Why Is My Fiberglass Pool Turning White or Fading?

A white, chalky haze on a fiberglass pool is often not calcium scale. It is usually chalking, a breakdown of the gelcoat surface. Fading is a slow loss of color from sun and water over many years.

Orenda, a pool chemistry company, has worked with fiberglass makers to study this in the lab. Their chalking research suggests the white material is a form of calcium bonding within the gelcoat, not sitting on top of it. That is why scrubbing and acid often fail to remove it.

Here is where Jason does something most Tulsa builders will not. He tiles every fiberglass pool he builds.

The waterline shows wear first. It gets the most sun, splash, and sunscreen. A band of tile covers that zone. It also makes a fiberglass pool look like a custom gunite pool.

Tiling fiberglass is slow work. Jason sets a level line around the pool with a transit, and each tile goes on by hand from a float in the water. That is part of why a Silverado fiberglass plunge pool starts at $45,000.

Solution: Mild dullness can sometimes be polished out with a fiberglass-safe compound. Deep chalking may need resurfacing.

What Causes Stains on a Fiberglass Pool?

Stains on fiberglass come from metals, organic debris, or scale. The color usually tells you which.

Most stains trace back to water balance. The CDC's pool operator guidance keeps pH between 7.0 and 7.8 for public pools. Jason aims tighter for home pools, at 7.2 to 7.6. When pH runs high, calcium falls out of the water and sticks to the walls. When it runs low, the water gets aggressive on surfaces and metal parts.

The Pool and Hot Tub Alliance publishes free PHTA fact sheets that explain each chemistry number in plain terms. Silverado Rock is a PHTA member.

Salt pools need extra attention here. A salt system tends to raise pH, so you'll need to add acid often. Our guide to saltwater vs chlorine covers what that means for your weekly routine.

One warning. If your pool runs on a copper-based mineral system, do not add a metal remover without calling the maker first. PristineBlue's FAQ says exactly that, because a metal remover strips the copper doing the work.

Solution: Test first, then treat. Never use a wire brush, steel wool, or an abrasive pad on fiberglass. Use a soft nylon brush. Scratches from the wrong tool hold stains and dirt.

Is My Fiberglass Pool Leaking?

Every pool loses water to evaporation in an Oklahoma July. A leak is loss beyond that. Check the fittings, skimmer, lights, and buried pipes before you blame the shell.

Try the bucket test:

1. Fill a bucket with pool water and set it on a step so the levels match.
2. Mark the level inside the bucket and on the pool wall.
3. Turn off the pump and wait 24 hours, then compare the two drops.

If the pool dropped more than the bucket, you likely leak. Run it again with the pump on. Worse loss with the pump running points to the pressure-side plumbing.

Solution: A pro can dye-test the fittings and pressure-test the lines. They can also fix a fitting leak without touching the shell.

What Do Fiberglass Pool Repairs Cost?

Repair cost depends on the problem. Surface repairs are cheap. Groundwork is not.

Let me explain the math that matters most.

Jason tells owners to test the water twice a month. That is 24 tests a year. At 10 minutes each, that is four hours a year. Four hours of testing on one side. A $6,500 resurfacing on the other.

Prevention is cheap. For what a new fiberglass pool costs to build the right way, see our breakdown of fiberglass pool cost in Tulsa.

What Most People Get Wrong About Fiberglass Pool Problems

Mistake 1: "Fiberglass is maintenance-free." It is low maintenance, but that's not the same as maintenance-free. You still test the water, brush the walls, and keep the pool full.

Mistake 2: "The warranty covers everything." A shell warranty covers the shell. It does not cover sand that washes away, a deck that cracks, or a fitting that leaks. The install is on the builder.

Mistake 3: "All fiberglass pools are the same." The resin inside the shell, the stone behind it, and the drainage around it vary by builder. Those three things decide how the pool holds up.

How Do You Prevent Fiberglass Pool Problems Before You Build?

The best time to prevent fiberglass pool problems is before you dig the hole. Ask these questions before you sign.

• What do you set the shell on, and what do you backfill with? You want crushed stone, compacted. Not sand. Not native dirt.
• How do you handle groundwater? Your builder needs a way to pump water away from the shell.
• What resin is in the shell? Ask for vinyl ester in every layer, backed by a lifetime structural osmosis warranty.
• Do you tile the waterline? Tile protects the zone that wears first.
• Who teaches me to care for it? You should leave with a clear water routine.
• Who shows up if something goes wrong? Get a name, not a phone tree.

Want to see how the work should go? Our guide to the installation process walks through every stage, including the backfill step, so you don't skip it.

Have a quote? Send it to Jason.

What Jason Recommends

Here's what I tell every fiberglass buyer. The shell you pick matters. The ground you put it in matters more.

When I started chip setting fiberglass pools in Tulsa, nobody else around here was doing it. It cost me more on every job. It made my quotes higher than the next guy's. But I'd rather explain my price once than explain a sunken pool for the next 20 years.

That Broken Arrow pool with the empty cavity? The owners didn't buy a bad shell. They bought a bad install. The sand left, and the pool and deck followed.

So I do three things on every fiberglass build. I set the shell on chip stone and backfill it with chip stone. I add plumbing so I can pump groundwater away from the pool. And I tile the waterline so the pool still looks right in year 15.

If you already own a fiberglass pool and you're seeing any of the problems in this guide, don't drain it. Take a photo and send it to me. I'll tell you straight whether it's cosmetic or something you need to deal with now.

Frequently Asked Questions

What is the most common problem with fiberglass pools?

The most common fiberglass pool problems are surface issues like chalking, fading, and stains. They are cosmetic and usually tied to water balance. The most expensive problems are a settling shell and a bowing wall. Both almost always trace back to poor backfill, like sand or native dirt, instead of compacted stone.

Can a cracked fiberglass pool be repaired?

Yes. You can patch surface cracks in the gelcoat. National benchmarks put a gelcoat patch at $300 to $400. A crack that goes through the fiberglass layers is structural and needs a pro. A new patch may look brighter than the older, sun-faded gelcoat around it.

Can a settled fiberglass pool be fixed?

Not fully. Once the backfill under or behind a fiberglass shell washes out, there is no real fix with the pool in the ground. A pro can fill the void with compacted stone to slow further movement. The real fix is compacted stone backfill before the pool goes in.

Why is my fiberglass pool turning white?

A white haze on fiberglass is often chalking, not calcium scale. Lab research from Orenda suggests chalking is calcium bonding within the gelcoat itself, which is why scrubbing and acid rarely remove it. Balanced water slows it down. Deep chalking may need resurfacing. Waterline tile hides the zone that shows it first.

Should I drain my fiberglass pool to clean it?

No. Never drain a fiberglass pool yourself. An empty shell is light, and groundwater can push it up or move its walls. You can fix green water, cloudy water, and most stains with the pool full. If a repair truly requires draining, hire a pro who pumps down the groundwater first.

Do fiberglass pools have problems in Oklahoma clay soil?

They can. Oklahoma clay swells when wet and shrinks when dry, which moves soft backfill around the shell. A fiberglass pool set on compacted chip stone, with a way to pump groundwater out, handles clay well. A pool backfilled with sand or native dirt is the one most likely to settle.

What should I ask a builder before buying a fiberglass pool?

Ask what the shell sits on and what fills the gap around it. Ask how the builder handles groundwater, what resin is in the shell, and whether the waterline gets tile. Then ask who you call if something goes wrong. Clear answers to all five tell you a lot.

Want to See a Fiberglass Pool Built to Last in Your Yard?

Fiberglass pool problems are real. Most of them are also preventable. The difference is what goes behind the shell, what goes under it, and who stands behind it after the water goes in.

Jason walks every yard himself before he recommends a pool type. The site visit is free.

Send us a photo of your backyard. We will show you what it can become.