How Low Should You Go?

[jheltibrand]

Hi all

I have a 18'x36' IG ~36,000 Gal with a 2 year-old vinyl liner. Last Spring when I opened I noticed some wrinkles/folds on the bottom on the shallow end. This past weekend when I opened there are more and larger wrinkles on the shallow end and the liner is obviously stretched on the walls. My thought is that I am possibly draining too low and taking pressure off of the sides allowing the liner to stretch (though I don't understand how this would result in the wrinkles.)
I've been lowering the water to just below the jets which happen to be about 3/4 to 1 foot below the bottom of the skimmer box. In all, this leaves only about 2' of water on the shallow end.
My question comes down to this: Is it OK to leave the jets underwater? Can I just plug them and siphon out the water from the lines and lower to just below the skimmer box?
Climate is St. Louis MO where winters can be anything from Arctic to tropical.

[JohnT]

I don't think your issue has to do with water level. pH below 7.0 can cause the liner to become larger and introduce wrinkles. You might want to recheck your pool's capacity. 18X36 with a shallow end is probably not 36,000 gallons. Probably closer to half of that.

To answer your question, you don't have to drop the water below the returns. Drop it to the bottom of the skimmer, then blow out the returns. You do this by loosely capping them and letting them each bubble for a while before tightening them.

[jheltibrand]

Thanks!

My ph was below 7 when I tested after pulling the cover off.

So you think it is about 18,000 gallons? It's 3'6" on the shallow end then at about 8 feet it slopes down to 9'6". My public school math skills calculated around 36,000 and that's what I've been basing my chemical applications on. Krikey!

Thanks for the advice!

[JohnT]

Thanks!

My ph was below 7 when I tested after pulling the cover off.

So you think it is about 18,000 gallons? It's 3'6" on the shallow end then at about 8 feet it slopes down to 9'6". My public school math skills calculated around 36,000 and that's what I've been basing my chemical applications on. Krikey!

Thanks for the advice!

It may be 24 or 25,000 gallons, but it's hard to say. 36K sounds really big. Excessive chlorine can cause liner issues as well.

[waste]

J, not that John's wrong in that the liner needs to be protected from acidic water!, but how's the water table in your yard & equally important, what's the winter snow/ rainfall? It kind of sounds like the liner might have floated, leaving behind the wrinkles. It seems to me that a chemical problem would appear ~ evenly throughout the pool, while a 'ground water' issue would be primarily confined to the shallow end, where the pool water is less.

[jheltibrand]

The liner in place when we moved into the house in Oct-04 (which we replaced the following spring) was floating at the deep end that winter.
Yesterday I noticed that on the shallow end (where the wrinkles are occurring), the liner is not in contact with the side of the pool where the side transitions to the floor. We have had maybe an inch or two of rain in the last two days and have drainage issues around the pool.

[waste]

With a fairly new liner the wrinkles being confined to the shallow end floor points to something my boss calls 'surface water' (this is different from ground water in that it's the result of the winter snow meltoff and spring rains not being able to pass through the dirt surrounding the pool quickly enough so some 'puddles' at > the floor level while waiting to be absorbed which pushes the liner up-- ground water is what caused the deep end floating a few years ago, the water table in the pool area came up higher than the floor), if the yard or neighbor's yard slopes towards your pool, it's gonna keep happening until you can improve the drainage around the pool . I also assume that you have been keeping the pH > 7.0.

Back to the origional ?, which I overlooked in my first response , with a high water table, or drainage issues - keep as much water in the pool as you can when you close! You can use a blower (many types) to evacuate the water from the lines and plug them while the air is still being forced through them without having to fear ice damage (whoever does the plugging will get wet ). If you want to be able to keep the water at ~ opperational level, they make 'blow through' skimmer freeze protection Gizzmos. The morre water in the pool, the better the liner will be able to resist the ground or surface water!