I am hoping someone can help me figure out why my DE filter pressure has fallen from 11 psi to 6 psi this week. I have not backwashed yet since opening and I would have expected a higher pressure. I have a 20K gallon gunite pool with Hayward pump and one return line leaving the skimmer. I have excellent water pressure leaving all of my jets, my skimmer has excellent suction, there is no air in the pump basket, I cleaned the pump basket that was full of pine needles, there was a little bit of air in the filter when I opened the pressure release valve.
I have just registered with this site, but have been following the GREAT information here since last season. This site has saved me from costly mistakes. I just bought my house with the pool in 2011 and only knew what the pool store told me. Needless to say, I always had algae appear, even when my chlorine levels were normal(which they weren't as later discovered). After reading the information here I have successfully lowered my CYA from well over 100 to 60 last season using higher chlorine levels and this season down to 25 CYA using lower chlorine levels. I discontinued using the Leslies pucks with CYA built in and only use sodium hypochlorite now. I never had an algae siting again after using the chemical guidelines used here.
Free Chlorine: 3.5 ppm
CC: 0 ppm
CYA 25 (might even be less)