Pool only leaking in winter - two years in a row

[AngelaKelly]

Last year we had a leak in the winter which started in January. In March, our pool guy cleaned the light and changed the gasket, put new plates around skimmers, and made sure the stairs were secure. He wanted to check all options before the liner. With those changes, we held water all summer! We had creases at bottom of liner due to the shift from ground water during the months that we couldn’t repair anything but that was it.

This fall, we closed in October and everything seemed fine until we woke up this weekend with a flooded yard and driveway. Our pool levels dropped, a lot and rapidly. We didn’t know how much water we would lose. We assume it’s the liner and received an estimate of 7-9k for a new liner.

After a couple of days, we noticed that the water stopped draining, at the same point this year as it did last winter.

My question, can something else be going on if the pool leaks only in winter to the exact spot, two years in a row? Or is this just a strange coincidence?

For reference, we do get a lot of ground water in our yard and had a lot of rain last week.

Here are pictures: last year’s leak (first set of pics, without cover), middle (with dog) shows pool over summer (holding water), and this year (same level with cover on and water loss).

Please note that we planned on purchasing a safety cover for this year but last summer we got hit with a new pump, filter, and salt cell all at once!

Any thoughts?

 

[ajw22]

You will get more views and comments if you post your pictures to the forum.

Picture Posting and Resizing - Further Reading

www.troublefreepool.com

 

[AngelaKelly]

You will get more views and comments if you post your pictures to the forum.

Picture Posting and Resizing - Further Reading

www.troublefreepool.com

Ok! I’ll have to resize.

 

[ajw22]

Ok! I’ll have to resize.

You need to get pics under 5MB for the forum.

 

[JohnT]

Wild guess, but maybe the water level got high enough the main drain pressure caused a siphon to start to the equipment pad and water flowed out until it equalized. Is your drain open to the pad during the winter?

 

[AngelaKelly]

Wild guess, but maybe the water level got high enough the main drain pressure caused a siphon to start to the equipment pad and water flowed out until it equalized. Is your drain open to the pad during the winter?

I am not sure. Do you mean what our filter is set to?

 

[JohnT]

I am not sure. Do you mean what our filter is set to?

Do you have a valve or plug closing your main drain line?

 

[AngelaKelly]

Do you have a valve or plug closing your main drain line?

A valve

 

[JohnT]

A valve

Are those valves closed now?

 

[AngelaKelly]

Are those valves closed now?

Yes, the pool has been winterized.

 

[wireform]

Not sure if this is even a thing....Do you have a hydrostatic valve and maybe it's stuck after significant high water table and is now equalizing with water table level.

 

[AngelaKelly]

Not sure if this is even a thing....Do you have a hydrostatic valve and maybe it's stuck after significant high water table and is now equalizing with water table level.

Our pool is vinyl. I do not believe vinyl pools have a hydrostatic valve.

 

[ajw22]

I don't see a hydrostatic valve in the pool's deep end in the picture.

Are there any penetrations in the liner lower than the pool light?

How old is the liner?

 

[InyoRich]

I'm really sorry to see this, and I'm completely befuddled by it, especially since it happened 2 years in a row. To break this down a bit, you stated a few things:
"we woke up this weekend with a flooded yard and driveway. Our pool levels dropped, a lot and rapidly. After a couple of days, we noticed that the water stopped draining, at the same point this year as it did last winter. For reference, we do get a lot of ground water in our yard and had a lot of rain last week."

What is the slope of your yard? I would assume, if you had a lot of rain, the pool would be overfull. Do you have an automatic cover pump on it?
The yard and driveway were flooded. Could your equipment have a freeze-protection feature that, somehow, turned on the pump and discharged the water through the waste valve? I know your weather intimately - I grew up in Latham - so I'm sure you have already had some cold days that should have turned on freeze protection if you have it.

My knee-jerk reaction would be to suspect the gasket at the light, since that seems to be where the water level dropped to, but I can't imagine how that would cause your driveway to get flooded.

 

[JohnT]

Yes, the pool has been winterized.

My hunch is it must be plumbing related, but I can’t say how. Somehow the extra water triggered the discharge. I’d think if the leak was below grade it would be slower.

 

[ajw22]

My hunch is it must be plumbing related, but I can’t say how. Somehow the extra water triggered the discharge. I’d think if the leak was below grade it would be slower.

There is no visible intake into the plumbing to get the water down to the level shown.

 

[Bill1974]

To have that much water escape that quickly it should be noticeable that a small lake is forming in your yard indicating something is up.

Is there a drain under the liner prevent the liner from floating? if it's routed in a way that it can act as a siphon once it gets going there is nothing to stop it. At the same time the liner has a leak and the pool shell is good enough to hold the water.

Are there any light or returns on the steps or shallow end?

Some photos of the yard and slopes may help figuring this out. In stead of sealing off all returns and lines I would leave them open to atmosphere to limit the possibilty of a siphon from happening.

Do you have an overflow?

 

[wireform]

So let me tell you a similar experience with a pool and the outcome, IG 25k vinyl, Season 2023 ended I winterized, as usual lowered below returns, cleared lines..expansion plugs...and tarp cover w/water bags. Fast forward..opening spring 2024 and with all the winter precip the water was down another 15"-18" from closing level. Uncovered pool and filled up the water to mid skimmer and called my diver, advised to clean up the water to perfect chemistry so there's good clarity for inspection. To my surprise I never contacted the diver because water level remained. Fast forward ...pool was used all summer with the typical evaportion that I had with other pools. Pool was used till end of September and then sat unused but with eqipment running monitered by the home owner. End of October I go to close and find the water down some 15"-!8" and green. I call the diver and ask how to proceed as I'm not closing a pool with an unknown resolve, advised same as in the spring so I filled back up and brought the water back to pristine and was topping up the water every few days. Had the diver do his thing, he pressure tested all lines including main drain and found it to be 100%. He did find a hole on the hopper floor in the 8 foot depth he patched. I will pass by in the coming days to see water level but this guy hasn't ever let me down.

 

[wireform]

My knee-jerk reaction would be to suspect the gasket at the light, since that seems to be where the water level dropped to

Clearly not the light as the level is below the light in the picture.

 

[JohnT]

There is no visible intake into the plumbing to get the water down to the level shown.

Main drain. If the outlet is below the water level, even if it goes up at the pad, it can drain the pool down to the level of the outlet. The primary difference in summer and winter is the way the plumbing is configured at the pad, so that seems the first place to look. Otherwise I can’t even come up with a wild guess of what could make the pool hold water perfectly during the summer, then suddenly dump a bunch at once in the winter.