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Top 5 Fiberglass Pool Problems and Solutions

Posted by Jason Hughes

By Jason Hughes

If you're considering the purchase of an inground fiberglass pool and done any research on the web, you've probably come in contact with some discussion of the problems associated with fiberglass pools.   The purpose of this article is to address, with full disclosure, five of the most common problems associated with fiberglass pools.....but we won't leave you there.  We'll also discuss the causes of these problems and how you, the consumer, can avoid them.  At River Pools and Spas in Virginia we have had the opportunity to install over 650 inground fiberglass pools.  Yes, that's a lot and No, every job did not go perfectly.  But because of the sheer volume of pools we’ve installed, plus literally hundreds of conversations with fiberglass pool manufacturers and installers from all around the world, we have an intimate knowledge of the good, the bad, and the ugly of inground fiberglass pools.  Congratulations, now we can share this information with you in the hopes that you'll never end up on one of those online swimming pool forums pleading for help.

Problem #1:  Repairs on colored fiberglass pools

fiberglass pool colored finishColored fiberglass pools are gorgeous...there's no doubt about it, and most manufacturers now offer a variety of colors beyond the standard white and baby blue marine gel coat.  The problem simply stated is this: If a need arises to do a repair to the pool, it can be difficult to match some colored finishes with the factory finish.    

The reality is that the vast majority of fiberglass pools do not need repairs, at least within the first twenty to forty years.  However, sometimes issues that merit repair work do arise, from something as small as a rock flying up and hitting the pool during shipping to a massive structural crack.  Granted these instances are very, very rare, but they do happen.  So you're probably asking "what's the solution?" 

Well, we can't change the fact that some fiberglass pools are going to need repairs for one reason or another, but to lower the risk of having a terrible looking repair you should look for one thing:  a solid surface finish.

Some colored finishes are applied in multiple layers (solid color, metallic flake, and clear coat for example.)  These layers overlap each other to achieve the desired look.  However, when a field repair is attempted with these muli-layered finishes, matching the factory look is difficult because it’s impossible to duplicate the manufacturing process.   

In contrast, a solid surface finish is applied in a single application which makes field repairs to fiberglass pool gel coat a lot less daunting.  Typically these repairs are a closer match to the factory finish.  If this is an important issue to you, research the various fiberglass pool manufacturers to determine if their colored finish is a solid surface or multi-layered finish. 

PROBLEM:  Repairs on Colored Finishes Conspicuous

SOLUTION: Solid Surface Colored Finish


Problem #2:  Spider Cracks in Gel coat

fiberglass pool gel coat cracksSpider cracks have always been an accepted part of fiberglass products.  But what exactly is a spider crack?  Spider cracks are hairline cracks that occur in the surface layer, or gel coat, of any fiberglass product.  They are not structural in nature as the crack is normally only through the thin layer of gel coat and do not extend into the structural laminate layers of the pool.  The origin of the name spider crack stems from the manner in which some of the cracks begin in a center point and branch out like the spokes of a wheel.   But to fully address this issue, we need to ask two questions:  What causes gel coat cracks and what can be done to prevent them? 

What causes gel coat cracks in fiberglass pools?

Gel coat spider cracks in fiberglass pools are a result of pressure on a given point of the pool shell that exceeds the gel coats ability to flex.   This pressure could be a result of improper shipping, improper manufacturing, or improper installation.  We've had pools by other manufacturers that were simply built too thin and couldn't withstand the pressures of lifting and shipping.  They arrived on the job site with gel coat cracks, and unfortunately, we had to send them back.  We've received pools that were built correctly but not stabilized properly during shipping with the same result.  But the most common human error that leads to gel coat cracks occurs during installation.  Sometimes a protrusion on the pool floor of the pool like a tree root or clump of dirt(neither should be there) exert enough pressure to cause a spider crack in the gel coat.  This occurs occasionally, but the most common cause of pressure on the floor of a fiberglass pool comes from the installer's attempts to level the pool shell.  Many times fiberglass pool installers are forced to attempt to level a pool shell that is 2"-3" out of level despite their best efforts to modify the base that the pool rests on.  This is done by lifting and tweaking the pool shell until they get it within a tolerable range.  This exerts a tremendous amount of pressure on the pool that sometimes results in gel coat cracks that can happen immediately or eventually develop over time.  In reality, this problem stems from a pool shell that is not built level, so the fault in this case lies with manufacturer rather than the installer.

What can be done to prevent gel coat spider cracks in fiberglass pools?

So what's the solution?  Find a manufacturer that makes level pools and a reputable contractor who will perform a proper installation.  To determine the “levelness” of a manufacturers pool shells contact a few of their dealers and ask them point bank, “How level are their pool shells?”  You could also contact some existing customers of both the contractor and the pool manufacturer you’re considering.  It’s a good idea to contact recent customers as well as those whose pools have been installed for more than five years.  This will give you a good idea of how the pool will hold up over time.   

ROBLEM:  Spider cracks in gel coat

SOLUTION:  Find a well manufactured pool and a great installer


Problem #3:  Pool Walls bulging

describe the imageIf you talk to enough people or scroll through enough on line forums you'll probably come across someone who has developed a bulge in the wall of their fiberglass pool.  We encountered this problem years ago with several of our pools.  This caused us to scrutinize our installation process and thoroughly inspect the pools where these problems occurred.  What we found flies in the face of the standard and accepted method of installing fiberglass pools across the country.  The problem in our case stemmed from the backfill material that we used.....namely sand. 

Tens of thousands of fiberglass pools have been installed with sand backfill without incident, and most of our sand backfilled pools were fine as well.  But when the right (or wrong) combination of circumstances align, fiberglass pool walls can bulge. 

Question:  What happens to sand when it becomes saturated with water?  It liquefies.  That would be fine if the liquefied sand were resting against something other than fiberglass which is renowned for its flexibility.   Fiberglass pools are structurally engineered to remain full of water.  The outward pressure from the water works in conjunction with the structure of the pool to stabilize the vessel.  When sand liquefies it is heavier than the water on the inside of the pool and if the wall is not strong enough to maintain its shape a bulge develops.  High water tables as well as soils that hold water both lead to situations where a significant amount of water surrounds the pool structure and saturates the backfill material.  So does this mean that fiberglass pools are not suitable for installations with high water table or certain soils?  Quite the contrary; I would submit that there is no better pool to have in such circumstances.  You just need to make certain of two things.  First, that you're pool is strong enough to prevent bulges.  And second, that you eliminate the sand backfill and use gravel.  Is there a difference between the strength of fiberglass pools?  Yes, but from the perspective of the consumer it will be virtually impossible to rate the "bulge-ability" of the various pools on the market because all manufacturers claim to be the strongest and most stable.  The one thing you CAN control is the backfill material, and based on our experience, using gravel backfill is the only insurance against wall bulges in any situation with any pool.   Clean crushed blue stone ¾" or smaller is the gravel used in our installations because it has several distinct advantages over sand or even round pea gravel.  First, its properties do not change when it becomes saturated with water so it performs the same wet or dry.  This makes it ideal for any situation and especially in areas with a high water table or difficult soil conditions.  Second, the point on point friction that occurs between the pieces of gravel make it a very stable material on the sides of the pool; much better than saturated sand that liquefies or pea gravel that acts like little ball bearings.    Third, the gravel compacts upon placement unlike sand which needs to be placed in lifts and compacted with water.  This is further addressed in the discussion on plumbing problems below.  You will see that this is a major advantage as well.  Opponents to gravel backfill pitch against it by saying that it's a cheaper material and used in order to cut cost.  In reality it actually costs us significantly more to use gravel.  We feel it is well worth the investment because you can't put a price tag on peace of mind. 

PROBLEM:  Pool walls bulging

SOLUTION:  Gravel backfill


Problem #4:  Fading of Colored Fiberglass Pool Finishes

describe the imageYes, another gelcoat problem!  Are you seeing a trend?  Before we jump into the fading issue....why do you think 3 of the 5 most common problems with fiberglass pools are gelcoat issues?  The answer is "Because that's what you see!"  Most, not all, but most fiberglass pools are structurally sound and will remain so for a long time.  But the look of the pool is equally as important.  Who wants a pool that looks bad after 5 years?  Not me!  The reality is that some fiberglass pool surfaces fade more than others, but this is understandable.  If you made me stand in the sun eight months of the year and in full contact with chlorinated water I'd probably change color a little bit too.  No one said this stuff was easy!  Fortunately you are not necessarily condemned to a faded pool.  Here’s what I’d suggest:  call customers who’ve owned pools for five years or more and ask them how their pool is holding up.  This will weed out the bad ones and allow the cream to rise to the top.     

PROBLEM:  Fading of Colored Finish                       

SOLUTION:  Call Actual Pool Owners for Feedback        


Problem #5:  Plumbing Settling causing Leaks

Why would the plumbing settle?  Good question!  The plumbing doesn't settle, the backfill material around the fiberglass pool settles and takes the plumbing with it.  Yes we're back to our sand vs. gravel discussion again.  This is great because this is a topic that needs attention.  The problem is that it's very difficult to fully compact sand around a fiberglass pool during installation.  Many times, despite a fiberglass pool installer's best efforts to bring the sand up in 6"-12" lifts and fully saturate the sand with water, the sand still settles some over time.  The plumbing is encased in this sand and as the sand settles, it exerts downward pressure on the plumbing of the swimming pool.  Many installers tie their plumbing up to help hold it in place, but not withstanding, that's still a lot of pressure.  Settled plumbing manifests itself in one way....leaks.  "Leak" is a dirty word!  We want to avoid saying that word, and we do so by using gravel backfill that just doesn't settle!  If the backfill doesn't move, the plumbing doesn't move.  It's as simple as that!

PROBLEM:  Leaks from settled plumbing

SOLUTION:  Gravel backfill

*If you liked this article, you may also find the following articles extremely informative:

Installing a Fiberglass Pool Properly: Sand vs Gravel, Which is Better?

7 Deadly Sins of Fiberglass Pool Installations

It's not mere coincidence that we have legitimate solutions to the top 5 problems associated with fiberglass pools.  At River Pools and Spas we constantly scrutinize our products and processes to eliminate any potential problems and make life easier for everyone.  You want to enjoy a problem free pool for years to come and it is our goal to make that a reality.  For more information about inground fiberglass pools visit www.riverpoolsandspas.com  and www.PoolSchool.us


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