Well I cleaned the filter -- it was pretty dirty -- and then took readings for the PSI and GPM for a given RPM. The table and chart are below. The "cleaner" pump is probably a good reference since it has no filter to pass thru, just a skimmer basket with a fine mesh sock. The "filter" pump pushes water thru the filter and you can see its flow rates are quite a bit lower. Is this normal or am I looking at replacing the filter cartridges?You should clean the filter.