I added DE to my sand filter---enough to raise pressure 1 psi (from 10 psi to 11 psi). This took 7 cups DE---I have a larger sand filter. For the rest of that day, the pressure crept up slowly, as the pool got noticeably clearer---nice! By the end of the day the pressure got up to 18 psi, and I anticipated backwashing the next day. But when the pump started the next morning (timer shuts it off at night), the pressure was back to ~12 psi, without a backwash! Is this normal? I wonder why the pressure dropped. Pump speed and valve settings did not change.
Big improvement in pool clarity, but I'm curious about the pressure.
Also, I assume all the DE is flushed out whenever I do a backwash?
Thanks for any info--