I just replaced my old 4 cartridge filters (Pentair -model# 17-8580) with new Unicel # C-7470. I nozzle spray cleaned the old ones about a month ago then re-installed them a began turning turning my pool from green back to sparkling clear. So the old, spray cleaned filters ran for a month after the pool was clean. I just replaced the old ones with the new Unicel filters. Just before I opened the filter housing the running PSI was 18". The PSI is 20" after I installed the new filters. Is this normal?
Thanks in advance!