Can't find leak, going crazy

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DaveFL

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Sep 17, 2011
3
In-ground cement pool. I have plugged all of the pipes (suction and return) besides the main drain suction hole and the pool is still leaking. I took the light out and saw that they had previously used epoxy on the light niche. I put an entire new layer of epoxy all around that. I then unscrewed the main drain (which was very fun considering that one of the screws was stripped). The main drain is made of plastic. There is a 2" pipe on the side of the main drain that is open. There is also a plug down there that I believe is the "hydrostatic release valve" which as I understand it needs to be opened when pumping the pool because it will allow water to enter the pool and prevent the pool from floating like a boat if there is water in the ground higher than the bottom of the pool.

In the main drain there is also this weird cement sand like mixture that was slathered along part of the drain's side, I guess to stop a previous leak. Some of it has fallen off and is sitting at the bottom of the main drain. I put a new layer of epoxy over this as well. I tried to dye test the light area and the main drain area but it was all unsuccessful.

The pool is still leaking. It has not yet reached the pool light so I cannot 100% rule that out. The water level is currently an inch or so above where the hole for the pool light starts.

This is my first pool and I had been refilling it liberally, finally realizing this was abnormal and not evaporation from the Florida Sun. The leak has been about an .75inch/24 hours for quite awhile, maybe a month. I have noticed that my sprinklers (well) have been very strong so I suppose there is a good bit of water down there. Tonight I ordered a 2" rubber plug online that I will use to plug the main drain. Some questions:

How big of a risk am I running the pool pops out of the ground? Do I need to unplug the "hydrostatic release valve"? What do I do from here I have no idea where the leak is coming from.
 
Welcome to TFP!

Hydrostatic valves are normally spring loaded and will open on their own when it is important for them to open. Sometimes people add a plug to keep a hydrostatic valve that is stuck open from leaking. The hydrostatic valve, if not plugged, will prevent your pool from floating out of the ground, unless it is stuck closed (which is rare/unusual). One possibility to watch out for is that the plug might not be a hydrostatic valve. Sometimes there are extra openings in the drain fitting that lead no where and they are sometimes simply plugged instead of being properly sealed off.

I suspect that your "cement sand like mixture" is just concrete/poolcrete that got inside the drain fitting when the drain was being installed, and doesn't have anything to do with your leak.

One way to get clues to where the leak might be is to keep close track of how much water you lose each day as the level goes down. When you are getting close to the depth of the leak the rate of water loss will slow down significantly.
 
I see that there are like little air bubbles on the top of the steel pool light cage and on the pool light rope (the light in on the deck of the pool out of the water) is this a sign that there is a leak still at the light niche or somewhere else in the pool light area?
 
I have a similar experience.

I noticed my pool was losing about 8-9mm of water (~1/3”) above evaporation rate. I checked it with the pump and without pump running – no significant difference. I plugged the skimmer and all the returns – no significant difference in the rate loss. I let it drop below the skimmer and returns (except the dead plugged one) – no significant difference again.

After it went down below the plugged dead return it slowed down to 5-6mm per day. I opened the return and it was full of water. I was hoping that I found at least one source of the leak, so I decided to reseal it better. I plugged it with rubber expandable plug and then put a regular winter plug over it. There was some rain right after that, the levels went over the dead return and it seemed that it held it. But now I’m doubtful since if there was a good leak there it would let the water out of the return when the water dropped past it.

I then turned my attention to the light. I want to get rid of it for future, so I decided to pull the cord and seal the conduit shut. I did and at that point for a day or two my rate of the water loss dropped to 2-3mms, which was significant.

Well, I filled the pool back up and now I have the same significant loss, maybe 5-6mm per day. Now I think that I might have a leak somewhere close to the level that I let the water drop to.

I dye tested everything and found nothing. I think there is a minuscule leak in one of the returns but it’s not measurable. I plugged my main drain (including the valve) and again saw no difference.

I’m closing the pool this week and I will monitor the levels under my winter cover (I assume the water in the pool will be pushed to the level of the water on the cover) so I will see if it settles on the specific depth. I measured the key levels in my pool and compare the water level to those. Otherwise I will continue my hunt next season.
 
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