safe depth to drain vinyl pool w/vinyl stairs

[ScottsdaleSwim]

I'm getting ready to drain my inground vinyl lined pool at least halfway. My husband is freaking out that we shouldn't drain it. One place on the steps has pulled away slightly (actually our realtor did it when we were looking at the house, she had never seen a vinyl liner and wanted to see what was behind it) and continues to pull away even after we shove it back in there. But it's minor.
So here's my question. I know it's safe to drain it at least half way...but even with vinyl stairs?
He's got me totally paranoid that our pool will sink through the ground and suck us down with it!

I hate the coping btw, how hard it is to change that? Curious..

Thanks.

Oh, I'm draining because my cya is over 110 now.

[cheshamjim]

First, I'm new to this board and to PoolSolutions, so keep that in mind when reading this post. I'm answering because I have recent experience with partially draining my pool earlier this Spring. I know others will be along to give you the best advise.

Be veerrrry careful!!!. For reasons that are beside the point here, I drained my pool down about 18" from the normal water line (just under 6,000 gallons). When the vinyl liner began to billow inward significantly, I stopped immediately. Luckily, I didn't do any real damage and when I refilled the liner pretty much went back to its original position (except for a couple of minor wrinkles on the bottom).

I believe that ground water can cause real problems when draining a vinyl pool. I've even heard of vinyl liners floating right up out of their reinforcing walls. This is not good. Maybe ground water is not an issue in Scottsdale.

I too have CYA above 100. I'm simply maintaining a high chlorine content as recommended by Ben's Best Guess CYA chart http://www.poolforum.com/pf2/showthread.php?t=365. I'm going to live with my high CYA for the rest of this season, then when I reopen next Spring I'll see where my CYA stands. If its still unacceptably high, I'll drain some, but not all of my pool water.

I'll be following this thread with interest since you and I have the same reasons for wanting to drain our pools.

-Jim

[Phillbo]

there was a method posted here a while ago where you lay in a plastic sheet on the water. you then pump the water out from under the plastic and add water to the top.. basically you can pump out the bad water without a lot of mixing from the good.

[cheshamjim]

I remember that thread and was part of it. I think it was Watermom who suggested an oversize tarp could be laid across the pool and new water added to it. As the rate of incoming new water and outgoing old water are kept approximately the same, the tarp would form a membrane against the sides and bottom of the existing liner due to the weight of new water.

This really sounds like a good idea to me, but when I posted a new thread asking about the experiences of anyone who might have had success with this approach, I got no response -- either positive or negative.

I will probably be trying it next spring if my CYA doesn't come down over the winter (and from what I read in these forums, it most probably won't).

-Jim

[Watermom]

Actually, it was Al (Poconos) who suggested this method. Don't know if he actually has done it himself or not. Maybe he'll comment on it for you.

[ScottsdaleSwim]

I didn't drain this weekend hoping for more responses.

The tarp would have to be the size of the liner. It can't just be the length and width of the pool because you have to account for the depth...or at least half of the depth depending on the amount you needed to drain - and then some so that you can hold it down on the perimeter of the deck, otherwise it would slide into the pool.
I'm not sure I could find a tarp that large.