I have recently purchased a home with a 30,000 gal gunite pool with attached spa. I have never owned a pool before and am trying to trouble shoot a couple of problems that I think are interconnected.
1)DE flows back into the pool when the filter shuts off. (American Titan 536090)
2)Water flows out of the spa to equalize with the pool's water level when the filter shuts off.
Thus far, I have cleaned the filter and checked all the grids and replaced the check valve that was visible. The previous owners disabled the backwash, so that's gone and I'm not sure what to do about that. Should there be a check valve or flapper at the bottom of the DE filter to prevent backflow? I don't see anything down there and it seems reasonable that this could be the problem. I appreciate your comments.