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Common Fiberglass Installation Mistakes

Common Fiberglass Pool Installation Mistakes

Like anyone that has been in the pool business as long as I have been can honestly say that if it’s possible to make a mistake with a fiberglass pool we have probably done it, or at least seen it. Good news is we are quick learners and dont make the same mistake twice and even better at learning form others mistakes too.

As Pool Pros has evolved through the years, we have consistently made efforst to improve not only our fiberglass pool projects but those built by our competitors through constantly striving to inform potential pool owners of the lessons we have learned through our mistakes and those of other builders. Our goals are to:

Educate and empower potential pool owners with everything they need to make the most educated decision when it ocmes time to purchase a fiberglass pool.


No matter how well your pool builder built the pool, if the cantilvered concrete pool deck is of poor quality the entire project looks bad. We had a rude awaking on our first cantilevered pool deck when our concrete guy who had been pouring concrete for 30 plus years left us with a pock marked mess.

When the stegmeier forms were removed the day after the poor, we were shocked to find the edge filled with pits and

pock marks. We had to scramble to come up with a solution to this issue as it made the entire porject look horrible. While the concrete was still green enough we used a rub brick to knock down imperfections and used a slurry mix that was hand rubbed into the profile to fill in any voids and imperfections. While it took alot of work in the end it turned out great. This problem illustrates the fact that just because a concrete contractor may have a tremendous amount of experience, nothing can replace experience with disposable stegmeier forms.

We have learned several valuable lesson on those early projects that have saved us countless hour of work and improved the look of each pool deck.

1: Proper Form Installation: We have found that it requires 2 times the amount of tie wires recomended by stegmeier to hold the forms in place. It also help to tape the forms together with duct tape which also helps prevent the form ties from pulling through the form.

2: Concrete Placement: This is critical as the concrete has to be gently placed against the syrofoam forms or the form can be damaged and or pushed off the pool altoghter. After the concrete is placed a concrete vibrator is used to bring the cream to the face of the form. This revents the pock marks, voids and aggregate from ebing exposed at the edge of the coping.

3: Cantilevered Form Removal: We used to wait until the next day to strip forms and address imperfections. We however do that shortly after the deck is poured. It involves getting in the pool to remove the forms and fix the edge. This is a little tricky but is easier to work the concrete at this point since it has not cured at all and can be worked over with the styrofoam profile form from stegmeier immediatley.


This is the a very common mistake made by inexperienced builder. Every pool not just fiberglass pools need to have the ability to remove potential ground water and relieve hydrostatic pressure. This is beacuse every pool type is susceptible to floating if hydrostatic pressure can't be removed. If your pool does not have a system in place to remove ground water, it is at an elevated risk of damage from hydrostatic pressure.

Pool Pros uses a sump pit system in every in grund pool that we build. This system consists of a simpel 8" diamter schedule 40 pvc pipe that is perforated to allow ground water to flow into the

pipe. The top of the pipe is finsihed off in the pool deck with a skimmer lid so it blends in seemlessly with the rest of the pool and decking. When needed, this skimmer lid can be removed and a submersible pump can be lowered into the pipe to pump out any ground water. This is an inexpensive component that should never be overlooked.


Plumbing is a critical component that if done incorrectly can have costly consequences down the road.

1: Wall Fittings

The biggest issue with leaks on fiberglass pools tends to be the return fittings. If you look at the fittings to the right, it is the Hayward SP1029 return fitting. While it is a great wall fitting for an above ground pools, it should not be used on a fiberglass pool. The simple reason is that the nut on the back is 1" wide and cannot be tighten correctly without it popping off the threads. If this fitting recieves any type of stress from gorund movement it will break or lose its seal causing a leak.The second picture to the right is the fiberglass wall fitting from CMP. It has a 3" wide nut that can be seucrely tightened to the fiberglass pool wall with no issue. You also dont wan

t to use the

​ gaskets that came with these return fittings. It is recomeneded to use a high quality silicone in place of a gasket to get the proper seal. Also dont forget to sand the outside of the fiberglass pool wall to get a smooth surface for a good seal.

2: Plumbing Support

It is critical to properly support your pool plumbing during the installation process. Having plumbing hanging horizontally from your pool puts undue stress on wall fittings and can cuase leaks. That is why at Pool Pros we plumb all of our pool

vertically down from the wall fittings to the base of the pool. We then run the plumbing along the compacted base of the pool. So as the gravel backfill is being placed it will slide down the vertical pipe rather than across it. This elimiantes the potential for any undue stress on the plumbing.

3: Pressure Testing

This is something that is typically overlooked by inexperienced builders as it requires special

equipment that some builder just dont want to purcahse. Pressure testing is done to ensure that there are not leaks in the plumbing. Pool Pros pressure tests the pool after plumbing ans after backfilling but prior to pool deck installation to ensure that your pool plumbing is 100% leak free. If your builder does not pressure test your plumbing and a leak is found after the deck is poured, the plumbing will need to be exposed and repaired. This may reuqired pool deck removal to do so. Something a 30 minute test could have prevented.

4. Proper Materials

At Pool Pros we use only schedule 40 rigid pvc. We use 2" for pool plumbing and for spa suction lines we use 3" to get the increased flow rates to provide power to therapy jets in spas. The reason we use rigid pvc is that is is rated for direct burial and pressure applications. Flex pipe is quick and easy but is not rated for burial and due to its soft nature can more easily be punctured by gravel backfill causing small pinhole leaks in plumbing. Also if flex pipe is used on a suction side system it can collapse under the pressure of the suction created by the pool pump.


The greatest advantage of fiberglass pools are the many differing seting benches, tanning ledges, steps, etc. The down side is if these are not backfilled properly it can lead to costly repairs. With our Tundra Loc System we have all but eliminated these issues.

1: In a fiberglass pool with a large bench, seat or tanning ledge we use landscape timbers and bottle jacks to keep these

heavy benches from sagging below level while backfilling the pool. While backfilling the pool we use 3/4 clean stone and good ol hard work and effort to pack the gravel under each and every step and becnh in the pool. We often use 2x4's and mini shovels to place the gravel under the steps and pack it in tightly. While this packing of steps and benches occurs we also are filling the pool with water and monitor the elevation of the these bench areas to ensure that they are still level. If needed we can make slight adjustments to the elevation with bottle jacks that we permanentley leave in place.

2. Another problem that occurs on straight wall pools is that the walls will bow in or out. The key is to run a string line from corner to corner of the pool and constantly monitor the walls during the backfill process; using the pressure of the water inside the pool or the backfill material outside the pool to achieve a perfectly straight wall.


While there is no such thing as a level yard, this is not the time to cut corners to grade out the pool area. If you have on eside of your pool that needs to be raised to get the elevation up, dont use the dirt that came from diggin your pool and here is why.

1. Your soil hasnt been tested and is likely unsuitable to support the weight of a patio or pool deck.

2. If the soil is good, it’s very, very difficult to compact the soil to an acceptable level.

3. In my experience the probability is hgih that there will be settling issues down the road. What may save you a few hundred dollars now can cost you thousand in a few years. This settlign typically takes place long after the workmanship portion of the warranty of your builder has expired. At Pool Pros we will not do this beause we build pools to last a lifetime not 3-5 years.


The bset way to correctly set a fiberglass pool in my opinion is to ensure it is set level on the inita

l set. This is done by strictly following the dig specs from tha manufacturer. It is very difficult and costly to set, adjust, reset and adjust,etc. It pays huge dividends to take the extra time to fine tune the base the first time. Solid Process, Solid Results.


DO NOT, I REPEAT DO NOT use dirt dirt to back fill your pool. 3/4" clean gravel and sand (under the correct circumstances) should be used to backfill a fiberglass pool. dirt, clay,etc wont compact on placment and will settle. There is no way around it. Cutting costs buy using dirt as a backfill is only going to lead to you spending considerable money down the road to do it all over again when settling damages the pool, the deck and more!

Well, there you have it! The 7 most common errors made when building fiberglass pools.

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Green Bay, WI 

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  • This website contains an abundance of information that has been created over the last decade or more. Some of the content on this site may reflect prices, perspectives, processes, entities, and names that were relevant at the time but may not be as relevant today. Consumers should consult a Pool Pros associate for the most accurate and updated information based on the unique conditions of their property. Consumers should verify specifications with the installing Pool Pros rather than relying on the information on this website, which is not intended to be a final specification.

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