Mystery Leak

[Kati.b]

Hello all,

First post here and it's a doozy! We are newish pool owners. This is only our second full season with the pool. It's a San Juan Fiberglass pool. It's 15'11" x 39'7", 14,400 gallons. One skimmer, two main drains, two returns, two LED lights on opposite ends of the pool.

Now the problem...after some very heavy rain this winter we pulled back the corner of the cover to drop in our water pump to drain out some water. Imagine our surprise when we didn't see any water to pump out! We pulled the cover back further and found that the water level was almost flush with our second step. Which would be about 12 inches below the top of the pool. We did the bucket test and found out we are losing about 5-6 inches a week. The water level was below the skimmer and the returns but we were reluctant to let it drop below the lights since that would be pretty low.

We've had two leak detection companies come out and everything has checked out. The lines were all pressure tested and passed and there were no cracks in the shell. My suspicion has always been one of the lights however they were dye tested and didn't pull in any of the dye.

I am at a loss. It's incredibly frustrating, we are adding water every day which is messing up our chemistry of course. Is there something I'm missing? Is it possible that even though the lights didn't pull any of the dye that they could still be the culprit?

Thanks and pardon any ignorance in this post. Like I said, we are still learning all of the ins and outs of pool ownership and honestly aren't impressed so far!

Kati

 

[JohnT]

Welcome to TFP!

Have you looked around your equipment or where your waste line (assuming you have one) drains? Those points can gravity drain in certain circumstances and the water will stop at about the depth the lines are buried. That's typically about where your water level is.

 

[Texas Splash]

Hi Kati! Along with John's question, I'm curious to know what type of light do you have in your FB pool? I have 3 of the smaller LED-type. Are yours LED as well, or do you have more of the traditionally larger sized light fixtures?

Also, now would be a good time to update your signature with all of your pool information. You can do this by going to the top of the TFP web page (just under the Pool School button) and select "SETTINGS". On the next page look to the left for a menu bar that says, “MY SETTINGS” and go to "EDIT SIGNATURE" to enter your pool and equipment info there. It will help us later. This link may also help you: Pool School - Read This BEFORE You Post.

Nice to have you with us. Hopefully we can get enough thoughts together to help you find where the trouble is.

 

[Kati.b]

Thanks for the response! We don't have a waste line and there are no leaks at the equipment at all. I should probably mention that there is a very lush section of grass behind our pool that I suspect is where the water is draining. I'm half tempted to dig and just see if I can find it but it would require tearing down a retaining wall.

- - - Updated - - -

Hi Kati! Along with John's question, I'm curious to know what type of light do you have in your FB pool? I have 3 of the smaller LED-type. Are yours LED as well, or do you have more of the traditionally larger sized light fixtures?

Also, now would be a good time to update your signature with all of your pool information. You can do this by going to the top of the TFP web page (just under the Pool School button) and select "SETTINGS". On the next page look to the left for a menu bar that says, “MY SETTINGS” and go to "EDIT SIGNATURE" to enter your pool and equipment info there. It will help us later. This link may also help you: Pool School - Read This BEFORE You Post.

Nice to have you with us. Hopefully we can get enough thoughts together to help you find where the trouble is.

They are LED. I don't have much info on them beyond that. Will update my signature ASAP.

 

[Texas Splash]

Oooh. That lush grassy area could definitely be a clue. Not sure why it wasn't an area of interest when those leak detection teams visited. So did you folks winterize your pool this year, or simply cover it? Were any plumbing lines "plugged" that you know of during the off-season?

 

[Kati.b]

Oooh. That lush grassy area could definitely be a clue. Not sure why it wasn't an area of interest when those leak detection teams visited. So did you folks winterize your pool this year, or simply cover it? Were any plumbing lines "plugged" that you know of during the off-season?

We pointed out the grass to both companies. It was winterized by a company and everything that should be was blown out and plugged to my knowledge. But I guess my question is still...even if was winterized improperly and a line cracked, wouldn't it fail a pressure test?

 

[Texas Splash]

That's what has me confused. The pressure test(s) should've been key to finding a failure somewhere. Curious though, how did they plug the main drains for that test? Did someone go in the cold water and plug the drains?

But here's what you do know .... the water continues to drop, even after it went below the skimmer and return jets right? If so, then you know the leak has to be from a light(s) or one of the main drains still submerged. The water level will stop falling once it hits the point of origin, or as JohnT noted the same depth at which the item was buried.

 

[Kati.b]

That's what has me confused. The pressure test(s) should've been key to finding a failure somewhere. Curious though, how did they plug the main drains for that test? Did someone go in the cold water and plug the drains?

But here's what you do know .... the water continues to drop, even after it went below the skimmer and return jets right? If so, then you know the leak has to be from a light(s) or one of the main drains still submerged. The water level will stop falling once it hits the point of origin, or as JohnT noted the same depth at which the item was buried.

I asked my husband about the main drain. He said that he did not plug the main drain but just blew air in the lines and if air bubbled out through them he theorized that there was no leak in that plumbing. But that doesn't seem very fool proof to me because just because some air is coming out through the main drains doesn't mean some is also leaking out through a crack, right?? They also pulled the covers off and dye tested them.

If I let the water drain down to the main drain level I will have very little water in my pool. They are almost at the bottom of the pool. I could probably safely let it fall to the light level though and at least rule those out.

 

[Texas Splash]

Yeah, that main drain thing doesn't make sense to me either. Normally when a company closes a pool, they will blow-out those lines, then plug them to keep the antifreeze inside. Otherwise, what's the point? Same for pressure testing. It's called a pressure test because it's sealed-off.

You definitely don't want to drain that pool too low. Since you have no water circulation at the moment, water must be slowly seeping from either a light fixture, or a main drain. But the main drain will only leak as long (or to the same level) as the pool water level itself. Imagine the drain down low, then the plumbing rises closer to ground level.. So perhaps one of those pipes ruptured (possibly from the inadequate closing and purging of the lines), and now is seeping. The only way to know for sure is if someone could dive down and physically plug each drain and see if the water level stops dropping. The leak detection companies should've been able to look for this, but it sounds like they didn't bring their "A" game.

 

[gwegan]

I agree with Pat. You need to plug the main drain and see if that solves the problem. If that doesn't solve it you should probably let it drain down to below the lights and see if that solves it. I wouldn't drain it more than that.

 

[Kati.b]

If there was a leak in the main drain would it be pulling air into my pump? There are no air bubbles in the basket.

 

[Texas Splash]

That certainly is possible. Are you running your system and pulling suction only from the main drains? No air is a good sign. May not be totally out of the woods, but is better than full-blown bubbles. Still would be nice to plug those up, shut everything off, and see if she still loses water. Water's probably a tab bit chilly tough.

 

[Kati.b]

Revisiting this issue. It's been raining like crazy so we are just now able to plug the main drains and see if we continue to lose water. IF we find that our leak stops, can we keep both main drains plugged and continue to run the pool? Based on where the green grass is in the yard I think I know which of the drains would be leaking so could I just keep one plugged and unplug the other?

I have two main drains but they come together to one pipe that connects to the equipment. I wasn't sure if I could plug one drain, leave the other unplugged, and continue to run the pool with the MD valve open. Hoping this makes sense.

 

[JohnT]

It's unlikely that your drain plumbing is separate, so plugging one wouldn't help and would override the safety provided by two drains. Plumbing is normally either at the bottom of the pool or within a foot of the surface, so if you see green grass it may be worth your while to dig.

 

[Kati.b]

The vast majority of the plumbing is under concrete. Are the main drains necessary or can I just operate off the skimmer?

 

[Texas Splash]

You can just operate off of the skimmer if needed.