[pbustin]

About two weeks ago, when I closed my 15 x 30 above-ground pool, I did two things differently from last year:

1) Following the advice given by my local pool store, I dissolved the winter tabs in a bucket of hot water, dumped the contents in the pool, and filtered the pool. (Last year, I suspended the tabs in their two containers, and punctured holes in the containers per directions.)

2) I used clips to secure the cover, in addition to the wire and winch. Last winter, I did not apply the clips until the middle of winter, and even then, did not apply them to all of the pool side.

I would think that as a result of one or both of these differences, the following has occured: In one spot only (near where the steps, that had become coated in slime in spots, had been), there has grown a steady and expanding area of gas (or air?) under the cover. It now measures about a square foot.

Any idea what is causing this, and what if anything I need to do about it? Just FYI, I inflated and positioned a 10-foot "pillow" under the cover, and incidentally, probably inflated it more than I had last year.

It's also under somewhat more pressure from above, inasmuch as I also installed a mesh leaf cover that's tightly tied here and there to a rope line I secured around the deck and the base of the pool supports (as well as porch supports on the side opposite the deck).

I chose this method of securing the leaf cover rather than winching it in order to keep the leaves away from the pool cover water, and in order to help the wind clear the leaves and to help me brush them off the leaf cover.

In case it's relevant to my question: Two automatic pool cover pumps remove most of the water on the cover, with additional help from a manual weighted siphon-type pool cover drain.

[StaticFX]

Are you ssure its some sort of gas? I mean, the cover is not air tight... so could some wind have blown in and created a bubble?

I would think that if you had enough problems with your water that it is creating a gas... you water would be nasty green... and most likely have ducks frogs and fish in it lol. I'm not sure of course... but I can't see how this could happen.

[pbustin]

Sure, I guess it's possible. There seem to be a couple of other pockets, now that the cover is drying from the rain. I'll see. Thanks for the suggestion.