Sand filter question

[waldreps]

I just opened my pool for the first time in several years. It has been covered this whole time but there are a lot of leaves and gunk on the bottom. I drained the pool so that only the deep end has water in it. I scooped out all the leaves and gunk from the shallow end. They were in the shallow end because I had to dump them off the cover to get the cover out because it was so heavy. I've scooped what I can from the deep end. It's hard to scoop when I can see to the bottom. Anyway, I have been running my Pac-Fab PF-50 sand filter with the skimmer closed and the return just shooting into the deep end. It has been running fine with the pressure increasing as expected and then I'd backwash and it would go down. I've been through this cycle several times since yesterday. Just now, I went to backwash and hardly any water comes out of the waste hose. The water in the pump basket area doesn't move around too much. It acts as if the filter is clogged and won't backwash. I can pump to waste, recirculate, rinse and filter just fine but now backwash isn't working right. What can possibly cause my filter to not backwash? Please offer up some ideas. Thanks.

[Poconos]

The pressgure gauge measures the pressure at the filter input. What is it reading when you have the reduced flow backwash condition?
Offhand I don't have any ideas yet.
Al

[waldreps]

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.