At the end of last year I replaced my DE Filter with a sand filter. I have a 24k gallon pool but oversized the filter with a 27" to reduce maintenance. My expectations were that by doing so I'd only have to backwash once every 2 weeks. But to my surprise, I've never once had to backwash it at all this season. The pool was very dirty when I opened it, but it cleared out after a couple of weeks. It's been running for almost 3 months since. The PSI when I first turned it on (both this year and last) was around 12 PSI and it's stayed there ever since. The only time I've ever had to backwash was at the end of last season when I had algae that I tried vacuuming (not to waste). In that case the PSI jumped to 20 and after backwashing it dropped back to 12.
Don't get me wrong...I'm not complaining, but I am surprised so I wanted to double check to make sure it isn't possible that maybe the filter is broken and it's not actually filtering. Although...my water is always clear so that would be a surprise as well. Is this normal? I mean, the PSI hasn't risen at all. Maybe 1 or 2 PSI tops in 3 months.