Okay, so I opened the pool this year and (unlike last year when the pool was full) the water level was just below the top of the pool light (which is also about the same level as the horizontal portion of the step gasket). I did some testing and it didn't seem to go below that and so my initial thought was main drain damage about that far down, but there's more to this. We had a lot of snow melt over the pool so I know it wasn't a lack of precipitation that caused it. So began a months-long journey to locating a leak. At first I thought it was the pool light because when I replaced it I forgot to seal up where the cord goes out of the niche, so I got some Pool Putty and sealed it and filled the pool. Somehow I managed to get the pool filled, but then it quickly started leaking again, about 3/4-1.5" per day on a 16x36 oval pool, so not an insignificant amount of water at all. It didn't matter if the pump was on or off, so I thought it could be somehow I totally botched last year's close and all my lines had problems, or the pool light niche repair with the Pool Putty didn't take, or something else I hadn't considered. We had a LOT of rain this year and I had a couple instances of a floating liner because of all the groundwater, so we'd get all this rain and it would fill the pool but the groundwater would make the liner float and push it out and then about a day or so after the rain came the liner was back in place. We plugged the main drain as I thought it the most likely source of my problem, and it seemed for a short while that the water level then maintained day to day, so I said okay I've identified the problem now to put 15" of water back in the pool so I can turn on the pump and run it through only the skimmer. Got it filled back up after a good while, I'd say a week or two, and within two days of getting it a couple inches above the skimmer it was back below the skimmer, so I said what the heck and have been chasing this leak. My last activity was to have the main drain and both return jets plugged (it was already below the skimmer gasket so no need to seal that off) and see what happens. Well, it's still losing water, so I went in yesterday and looked and the pool putty in the light niche seems good, nothing obvious there, but then it struck me - what if it's the stairs? So that's basically where I'm at, but the problem with the stair leak is that it doesn't make sense given where the ground around the pool is very wet, all the time (guessing because it's leaking somewhere near that spot). In the attached picture, the wet spot in the lawn is red, the black spot is the pool light, and the purple spots are the returns. The main drain is down by the diving board (of course), and the skimmer is on the left (you can see the top plate by the slide). From what dye testing I have done I haven't seen anything obvious that would be pulling that kind of volume. Any help the group can provide (or other information you need to assist) would be greatly appreciated! With all the plumbing lines closed off I'm left with a structural issue but don't see any holes in the liner. For that kind of volume I've read it would be a hole about the size of a pencil. Additionally with the main drain plugged I've noticed the water level in the pipe over at the equipment pad has not been dropping so hoping to be able to cross that off the list of possible issues since I happen to like having the main drain so I can run the pool pump when the water isn't all the way up to skimmer level.
Leak Detection Theory, Assistance Please
- Thread starter MrBobC
- Start date
- Jun 22, 2014
- 52,086
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
In a case like this you have to take it slow and methodically one section at a time. One thing's for sure, if the water level stops at some point, you can almost bet the leak is around that lowered waterline. That's the area I would pay very close attention to all around the pool. You mentioned the stairs, and those can be troublesome, but it's interesting you noted the opposite end of the lawn wet in the red area by the equipment pad. 
No chance you have a multiport valve that is leaking to waste?
www.troublefreepool.com
No chance you have a multiport valve that is leaking to waste?
Leak Detection
A number of things can cause leaks in your pool. You can learn tricks for leak detection and how to pinpoint where your pool is losing water.
www.troublefreepool.com
I had a similar experience to yours. Same size pool. Same amount of water loss. In my case it was in fact the light niche leaking (maybe not your case with the wet area being the opposite of the light). One bit of advice I will give you is be patient. Especially with dye testing.
When you dye test the niche, be sure to have good lighting. Since it is set back, you dont get good light in there. Im a diver, so I have an underwater flash light. With out the light, it was very hard to the the dye getting sucked in. At the rate you are loosing water, the dye test may not be so obvious. Trust me when I say you need good light. With good light in the niche, I could see the dye barely going into the conduit hole.
When making my repair, all I had access to was the underwater two step epoxy. I made sure to let the epoxy set for several hours prior to setting the light back into the niche. Remember that pool putty will be flexible for a certain period of time. If you try to reset the light into the niche while the putty is still pliable, you could mess up your repair while moving the chord and dislodge your putty repair.
BE PATIENT!!!
Good luck
When you dye test the niche, be sure to have good lighting. Since it is set back, you dont get good light in there. Im a diver, so I have an underwater flash light. With out the light, it was very hard to the the dye getting sucked in. At the rate you are loosing water, the dye test may not be so obvious. Trust me when I say you need good light. With good light in the niche, I could see the dye barely going into the conduit hole.
When making my repair, all I had access to was the underwater two step epoxy. I made sure to let the epoxy set for several hours prior to setting the light back into the niche. Remember that pool putty will be flexible for a certain period of time. If you try to reset the light into the niche while the putty is still pliable, you could mess up your repair while moving the chord and dislodge your putty repair.
BE PATIENT!!!
Good luck
Definitely not the multiport. I get the same water loss when the pump isn't running as when it's on (leading me to think it's structural). Also, the multiport waste out is plumbed to go to the left of the concrete pad.In a case like this you have to take it slow and methodically one section at a time. One thing's for sure, if the water level stops at some point, you can almost bet the leak is around that lowered waterline. That's the area I would pay very close attention to all around the pool. You mentioned the stairs, and those can be troublesome, but it's interesting you noted the opposite end of the lawn wet in the red area by the equipment pad.
Leak Detection
A number of things can cause leaks in your pool. You can learn tricks for leak detection and how to pinpoint where your pool is losing water.
Thanks for the insight. I don't have an underwater flash light, and when I did the dye test I already had the light out of the niche. After using the Pool Putty I didn't move the light for probably a week or two (it sat on the deck above), so I don't think it was messed up while the putty was pliable. Having gone down under water and examining it (but not while doing a dye test, figured my going under would be enough to mess with the dye test results) it does not appear to have any areas missed with the Pool Putty. Recognizing it's a putty though I wonder if the underwater caulk would be a better match for it. I could do a dye test with a mirror perhaps... I will also add there is a LOT of caulk around the pool steps, basically all around the cover strips, around the cover strips, etc. Starting to make me wonder if they had a problem there before and just caulked the Crud out of it and now that it's been some time that "patch" is failing.
The thing that still stumps me is that it's consistently wet behind the equipment pad on the hill which is the farthest point from the steps and niche you can get. With the wetness of the soil that is behind that equipment pad it makes me want to jump to some kind of plumbing issue because that's where all the pipes are, but with all the lines plugged that means it can't be a plumbing issue, right?
Well it was a hole in the liner over where the ground was always wet, found it when I was brushing the walls.
One of my pools developed a leak, had a diver come in and found it in short order. Interestingly he used a double patch. The first was just over the the actual hole and the second one encapsulated the first patch for extra measure.