Losing water down main drain

[d-shard]

I realized last summer the pool had a leak. So die-hard diy-er myself set out to find it. Finally deduced it must be in the main drain after pipes held test pressure. Recently, we've been losing 2-3" of water per day unless I covered the drain which slowed the loss to 1/3" per day. I drained the pool yesterday/last night. Upon inspection of the drain this morning, I found the leak. The grate covering the drain sits in a one-inch thick ring, and there's another one-inch thick ring under that one. Then the drain cavity shaped like a big coffee can. Around the top of the can, just two inches below the floor of the pool, is a gap ranging from 1/8 to 1/4" wide. Beyond the gap is concrete, yet I observed water seeping in through that gap. I figure when there's water in the pool there's enough pressure to force water to go the other way and leak out of the pool. I removed the stopper in the bottom of the drain and water slowly rose to a point 1-1/2" below the leak level then stopped rising. See attached photo.

So, the delimma is how to fix the leak. I first thought of hydraulic cement but would that be a good choice with the drain vessel being PVC? Another option is I have a tube of IntheSwim nitrile caulk but I've never used this product so not sure if it would be a good choice. When I was doing pressure testing, I used Flex Paste to seal unconventional fitting pairings for my test rigs and it worked great. It doesn't harden but becomes very firm (especially in water) and when left to cure for 24 hours, I never observed it leaking and it plugged everything I asked of it. In this moment, I'm leaning toward that product based on my experience. Not sure about the long term, however. Then there's Pool Putty but I've never used that. May I please hear your ideas and opinions? Thank you!

 

[ajw22]

Welcome to TFP.

I would use pool putty or Plast-aid to fill the gap.

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Plast-aid is a multipurpose repair plastic used for countless applications. Plast-aid chemically fuses to some plastics like PVC ABS & acrylic and mechanically bonds to rough surfaces like wood, concrete, brick. It has a unique curing process that lets you cast glue fill form & becomes a hard...

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https://www.amazon.com/Atlas-Epoxy-Pool-Putty-Set/dp/B0002Z0NBY

Let's see what @1poolman1 @bradgray @Poolbreh would do?

 

[bradgray]

We use Plast-Aid almost exclusively on acrylic spas because we can sand it smooth. Good product. Stinks up the entire toolbox. Never used it on PVC leaks (we always just cut and replace) but it will chemically bond with most plastic, which would be the equivalent of a typical joint weld. I'd expect you'd find success with that. You're gonna need a fair bit of it given the size of your gap. It's also not flexible, so if the movement continues, you'll have another crack.

Never personally used Pool Putty, but it's a popular product. It's present on a couple of our clients skimmers where the PB had to layer collars together. Seems pretty solid. I do appreciate that it's almost like clay; the Plast-Aid will harden similarly as you work it but not quite to a clay-feel. It always stays fairly gritty like smashed skittles. I imagine Pool Putty could work as well or better in your situation since you can really mash it into the void and it may flex a little.

We also use 801 Silicone on fiberglass pools. The bond is so strong we've cracked/broken eyelets and faceplates trying to remove some bonded with it. 3M 5200 is another product we've used the same areas as the 801. These are probably the best bang for buck as far as product volume.

 

[JamesW]

PC-11® Paste Epoxy – Protective Coating Company

www.pcepoxy.com

 

[mknauss]

What about abandoning the drain all together? Not needed. Still plug the gap. And then plug the entire drain up. Leave it so you can replace the grate for looks.

 

[JoyfulNoise]

are you the original owner of this pool or did you inherit it? If it’s an inherited pool, then it looks like it was replastered at some point and the plaster applicator just put a new retaining ring on top of an old drain. It seems like you have a leaking main drain sump which is not easily or cheaply repairable. You can try all the plastic goops and glues to try to seal it but my bet is it will just start leaking again at some point. Water from above and behind it will eventually compromise any seal you make.

I’m with @mknauss … abandon the drain. Just fill it with hydraulic cement up to the cover ring. Then cut and cap the line at the pad of there is one.

 

[1poolman1]

Welcome to TFP.

I would use pool putty or Plast-aid to fill the gap.

Waterproof Plastic Repair Kits Fixes cracked ABS PVC Acrylic Wood More

Plast-aid is a multipurpose repair plastic used for countless applications. Plast-aid chemically fuses to some plastics like PVC ABS & acrylic and mechanically bonds to rough surfaces like wood, concrete, brick. It has a unique curing process that lets you cast glue fill form & becomes a hard...

www.plast-aid.com

https://www.amazon.com/Atlas-Epoxy-Pool-Putty-Set/dp/B0002Z0NBY

Let's see what @1poolman1 @bradgray @Poolbreh would do?

Hydraulic cement will fill the gap and bond the plastic. PlastAid (my favorite) will bond to the plastic as well. Would need to put a filler in the gap to keep it from flowing down and out. Even a rolled plastic grocery bag will work. Leave at least 1/8" to 1/4" open for the PlastAid to bond and it will last a very long time. Get the larger kit and mix it a little thick so you can hand apply it.