Like the subject says, I have a Nautilus FNS 60 DE filter on my pool. I have had the pool and filter for 8 years. I replaced the FNS grids last year. A couple of questions:

1. After backwashing the filter has about 14 psi of pressure. Before the DE is added, it goes up to over 30 psi in maybe 10 minutes. The pool is a bit cloudy but otherwise the water is good. I can backwash frequently but it does the same thing. Adding DE is a waste of $$ since it gets backwashed out 10 min later. I disassembled the filter, washed the grids thoroughly (no calcification that I could tell), reassembled, and it did it again.

2. The filter is making a continuous gurgling noise. I can see a bit of air in the clear cap of the pump strainer but I have never known it to make the filter gurgle. Yes, I bled off all the air in the filter.

3. The FNS User's Manual says to never run the filter more than 2 minutes without DE. Why? What damage will it do? As I said before, adding DE is a waste of money right now until I figure this problem out.

Thanks in advance for any advice you might have.

Chuck