thanks so much, I will do a bucket test in the next 1-2 days and let you know how it goes. Thanks for referring my post to PoolDoc also. I would be curious if anyone else has experienced "floaty" areas on the bottom of their pools. As far as I know this is a regular plaster pool (no liner), I had no idea that solid plaster could "bob up" the way these areas are, to the point I can push down with my hand and feel the "give". Maybe there is some flexibility of this material, even though normally it has a hard concrete feel to it. The first two pool steps going into the shallow end appear solid without any bobbing or floaty/squishy feel....once past the last step and down one the shallow floor is where these particular areas are found. I'm mystified! Thanks again! (btw, i made a typo in my earlier post - plastic, I meant to type plaster. There is no plastic or other vinyl material. It's ust a traditional plaster pool.