Thanks for the reply, Al. The gauge was reading almost nothing when trying to backwash and almost no water would come out of the waste hose. I decided that with all the muck that was in my pool, the sand must have gotten all clogged and couldn't backwash. Yesterday, I went to the pool store and bought new sand. I replaced it and now the filter is working great on filter and backwash. That must have been it. I didn't really think something like that would happen but apparently it did. I figured I'd try that as the sand was pretty cheap, and it was pretty easy to do. Also, I've lived here for 7 years without replacing the sand and who knows how long it had been since the last person did it. I'm sure it needed it.