Two months ago I installed a hayward pro grid 36 sqft de filter; I was replacing my old hayward sand filter. The pool has three returns, two skimmers, a main drain, a slide return, and a whisperflow 1 hp pump, 2" main piping.

With the sand filter the pressure would start at 20+ psi after backwashing but the 36 sqft de filter starts at 10 psi. During two months the de filter has been in operation the pressure has risen 1 psi. At this rate the filter will only have to be backwashed/cleaned once a season.

I was afraid of buying filter to small but so far the 36 sqft is doing great and the water flow in the pool is much stronger. Now the kids can swim in place against any of the return currents. Same pump same piping only the filter has changed and it made a very noticeable difference in flow.