This season I switched the motor on my superpump for a 2 speed one. After I opened the pool I experimented with my inline chlorinator to see how it would work on low speed (my CYA is low so I could use some trichlor&CYA in my pool).
It turns out that the flow is not strong enough and during my experiments the FC levels in the pool were border line low. So I got myself a nascent algae bloom Ė the water turned pretty hazy, but it didnít turn green. Mistakenly thinking that Iím not filtering enough, I tried to filter it all out. It worked to some extent.
Last season I backwashed 3 time for entire season (DE filter). This time to get rid of the haziness I backwashed 5 times in a course of 3 days! The pressure was going from 9psi to 20 psi in a matter of few hours. I figured something was wrong and realized that I need to shock it. So I shocked the pool and the water got back to normal.
During this ordeal I noticed something interesting. At the end of the shocking process, pressure on the filter was 16 psi in the middle of one day. I figured Iíd come home from work and back wash it again. When I got home, the pressure was 15 psi. The pump was on all this time, so it simply dropped during continuous pump operation. Sometimes pressure changes when the pump is stopped and started again but this was not the case.
Puzzled, I decided to let it run one more day. At the end of the next day the pressure was 12 psi. Next day even lower.
So Iím curious what process might result in the pressure on the filter coming down over time. First I thought that maybe my suction head loss increased so the filter gauge would read lower, but the pump vacuum gauge showed only small increased. Overall the flow improved from one day to another.
The FC levels were still around the shock level (not much sun last few days + cover), so could have FC eliminated (oxidized?) some dead algae in the filter? Would it work like that? Or is it a simple case of some DE settling on the filter grids?