Thanks so much for your reply. Looking at the strainer gasket, it doesn't look great. The pump basket does look a bit foamy. Is replacing the gasket very difficult? How would I replace the old one and install the new one? I do have some silicone stuff from when we changed the o-ring on the filter's dome. Here is a picture of what we have, and it's #4 that we would be replacing:

http://www.haywardnet.com/products/m.../Manual113.pdf

Oh, one other thing- the flapper door between the pool and the leaf skimmer - does it open completely when the filter is running, or just enough so that water comes in?