jmlodin said:
I didn't totally understand everything you said but it is good to know that number is reasonable! Now I will just watch for it to go up to 32-33 PSI before backwashing. Thank you so much for your expertise.
Sorry about that. Let me explain a little more. Using the pipe diameter, pipe lengths, filter PSI, pool pump head curve and a few other esitmates, I can predict with some accuracy what the operating point (i.e. GPM and head loss) is for a particular pool/plumbing combo. With your setup, the pump is probably delivering close to 69 GPM with a clean filter.
However, if you wait until 32 PSI, the pump will be delivering only about 45 GPM. This will increase the turnover time by 50% or for the same pump run time, it will decrease the amount of water being filtered by 35% so it is something to keep in mind.
A dirty filter might filter better but because of the increase in pressue, the pump won't filter as much water either. Also, running at a higher filter pressure means that the in-floor head pressure and flow rate will be lower so they may not work as well.
Given your situation, it might be better to clean the filter before reaching 30 PSI but it depends on your schedule and how often you are willing to clean the filter. Hopefully with a sand filter, backwashing a bit more often shouldn't be too much of a burden but it is entirely up to you.