Draining Fiberglass Pool to Fix Main Drain Leak

Liquid

Silver Supporter
May 11, 2023
28
Jacksonville, FL
Pool Size
4240
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 700
I have a 4,240 gallon San Juan Cyberlane with Spillover Spa (W 8’6” – L 23’ – D 4’9”) pool with a main drain leak which is on the outside of the main drain, as shown in the picture. This leak detection was done by a professional leak detection company. It’s nearly impossible to find someone who wants to work on a fiberglass pool and was only even able to get one company to give a quote for the repair, which was $5,500. My wife wants to get rid of the pool regardless and it was a firm “no” on $5,500, but said If I could do the repair then fine, lets keep it.

I obviously need to be able to access the drain dry so thought about two different methods to have access to the drain while not completely draining the pool. I have the benefit of a drainage area just off my property about 20 feet from the pool that tells me even after the heaviest rain the water table is about six inches below the bottom of my pool. The water table drops about another two feet in extended dry weather.

The first idea is somewhat simpler and it is to just get a bunch garbage cans, sink them upright in the pool. From there I would brace the pool using plywood against the walls and 2x4s across the mid sections. Then I would use a sump pump to drain the pool, leaving the garbage cans filled and giving me dry access to the return. Each 32 gallon garbage can full of water will weigh about 265 pounds.

My second thought would be to create a diagonal wall using 2x6 and plywood to create a triangular space by the leaking drain. It would go from about three foot out from the corner to about three foot out to the side of the pool, isolating the area of the drain leaving a triangular access. The wood would be mitered and shaped to perfectly fit the outline of the pool. I would also buy an oversized vinyl liner for an above ground pool. I would sink the liner in the pool, lay it out on the bottom of the pool, then covering up the walls and the temporary plywood wall in corner. From there, suck the water out of the corner of the pool, leaving that corner dry, water being held back by the liner.

The garbage cans seem simpler and is the way I am leaning but would love to hear any thoughts, comments or other feedback on either of the methods or an entirely different way to tackle this.

I will have other questions related to the repair, e.g., what parts to have on hand the day I do the repair, how to properly backfill as well as others, but wanted to first focus on the methodology to getting access to the drain. Thanks
 

Attachments

  • Leak Location.jpg
    Leak Location.jpg
    166.9 KB · Views: 25
  • Pool 1.jpg
    Pool 1.jpg
    632 KB · Views: 27
Yikes. We're getting into some serious math now. :hammer: Upwards pressure versus the weight from cans pressing downward, and are they adequate enough? That's beyond my skill set honestly. But you do have to address those two situations - upwards pressure and side movement as it's very possible the walls will try to bow inwards. I've seen contractors build braces that span the width of the shell in 3-4 places to prevent the bowing. I'm not sure about the garbage cans having enough counter-pressure against a potentially elevated water table. Of course if the table isn't actively rising, all is good. Places that know for sure the water is pressing upwards will drain a hole or two through the shell bottom to relieve that pressure - like removing a cork. Hopefully you won't have to do that.
 
Thanks for the feedback. Given that I can see when the water level is below the pool I was a little less concerned about the upward pressure and thinking about preventing the floor from buckling. I am going to go with the garbage can idea and brace the walls all around using two foot strips of 3/4 inch plywood and 2x4. From poking around the web it seems about half way up is the place to put the braces.

I assume that when I drain the pool the spa side will stay filled. Am I correct on that one?

Any thoughts as to what I should have purchased before draining the pool? Obviously a new drain. I believe it is piped 1.5 inch so will pick up some pipe and was planning on using Christy's Red Hot Pool Pro PVC Cement. A few sweep elbows. Anything else I should have on hand?

I know there is some debate as to using silicone vs a gasket when sealing the drains and was planning to go the silicone route. Any countering thoughts? I know I should be sanding the area smooth before installing the drain. How long would you normally wait before refilling?

I appreciate the guidance so I can keep my pool :cool:
 
You might want to call a place or two, and get a quote on removal. It will be many times what you would expect. There's the heavy equipment, the disposal of all the debris, the proper compaction of the new fill dirt, the permits and inspections your city likely requires. And then there is the relandscaping of your yard, both for the pool area, and all the damage done by the heavy equipment and the places they staged all the materials.
My wife was adamant about filling it in when we got very high quotes for replacing the 6' fence all around the yard. No pool, no need for the fence. Then the bids for filling arrived. We have the new fence, and have done other pool equipment updates. Even planning for big pool disasters, we will still be money ahead over the next many years. Here in Minn., pools aren't the best for resale value. One would think in Florida, that would be the opposite.
 
Any more specifics on where the leak is? Is it not something you could fix with underwater epoxy and a dye kit to make sure it is sealed?

Most FG pool plumbing I have worked on has a compression fitting that has to be tightened from the back of the pool shell. I don't think repairing the main drain is going to be as simple as draining the pool and swapping in a new drain.
 
  • Like
Reactions: Texas Splash
The leak company pressure tested the system and it was not from the inside. They mentioned that it was from the outside of that main drain, likely the screw in compression fitting being the culprit. They did a temporary epoxy repair but never really did much.

I don't think repairing the main drain is going to be as simple as draining the pool and swapping in a new drain.

@MAPR-Austin, Would you mind sharing a bit more as to why it may not be as easy as replacing that fitting? I'm trying my best to understand what I may be up against. Thanks
 
The leak company pressure tested the system and it was not from the inside. They mentioned that it was from the outside of that main drain, likely the screw in compression fitting being the culprit. They did a temporary epoxy repair but never really did much.



@MAPR-Austin, Would you mind sharing a bit more as to why it may not be as easy as replacing that fitting? I'm trying my best to understand what I may be up against. Thanks

I believe that the compression fitting is tightened from the backside of the wall, so you will need to not only drain the pool but excavate under the deck and down to where the main drain meets the wall. I think it goes: Main Drain Fitting with threaded fitting | gasket | pool wall | gasket | compression nut with slip fitting.

I would say keep the pool full and operating. Pull up some pavers and demo whatever is under them, then dig down to where the main drain goes through the wall. You might be able to just tighten the compression fitting that is there, and visually verify that it stops the leak since the pool will be full. This is a lot of labor but it is doable by anyone who is careful.

If you can't stop the leak and have to drain the pool, see if you have a dewatering line. This would be a pipe that is open down to the gravel bed under the pool. You can use that pipe to constantly remove water from under the pool.

Your trashcans full of water idea is clever, I think that will help a lot. Use wood braces as insurance.
 

Enjoying this content?

Support TFP with a donation.

Give Support
so you will need to not only drain the pool but excavate under the deck and down to where the main drain meets the wall.
I was resigned to this already. The pavers had started to sink so was going to redo them. The leak detector said the pool had to have been leaking a really long time for that to happen given the leak is on the bottom of the pool. Possibly since the install.

You might be able to just tighten the compression fitting that is there
This was my first thought though am fearful that once I dig down the pool will just empty out from the hole where the main drain is and then I dont have the pool braced. I'm half expecting that the installer forgot to cement the pipe going into the compression fitting.

see if you have a dewatering line
I dont have a dewatering line but know the water table is 6 inches below the bottom of my pool after heavy rain and more than two feet below after extended dry weather. There is a drainage area on the other side of my fence about 20 feet away from my pool where I dug to find the water table.
 
What if you no longer had a main drain?
Could you use a vacuum hose instead?
I'm not sure I follow the question. I know I don't actually need a main drain as I could use the skimmer, which is essentially what I do now as I have the main drains isolated from the system.