I've been struggling with water quality problems, and running the filter 24/7 for a couple weeks. The Forum has been invaluable in steering me in the right direction, and success seemed almost here.

But....

Friday I noted more of a drop in level than would be just evaporation, so I marked the pool level and set out a measuring cup filled to the one cup level. Saturday morning the pool was down by 3 inches, and below the skimmer inlet. Certainly not evaporation!

Since the liner is old - it has two tears above the water line, I suspected a liner leak. Since the water was still cloudy, I added some flocculant from Leslie's Saturday afternoon so that perhaps I could see a problem area. It calls for 2 hours of recirculation, then no filtration for 1 or 2 days. I also marked the water level when I shut off the pump.

This morning there was no perceptible drop in water level.

I suspect a leak in the pressure side, which naturally runs under the concrete pool surround, and comes up through the concrete slab in the poolhouse. Does anyone have any experience in dealing with this sort of problem? I know that radiator leaks can be fixed, at least temporarily, with various additives. I hesitate to replace the liner before this newest problem is fixed.

The pool is inground, about 25K gallons.
Sand filter, 1 hp pump.

Thanks for any advice.