When I run my pump at 1000 RPM, the filter reads 0 PSI even though my flow meter shows water moving at about 15 GPM. At 2000 RPM the needle moves up to 5 PSI (35 GPM). At 3450 RPM it was 20 PSI last time I cleaned the filter ; today it's 24 PSI. I don't ever see an increase in PSI at the lower RPM's; I need to ramp the speed up to maximum in order to gauge when I will need to clean the filter again. Does this sound like normal operation and is there any disadvantage to running the filter at 0 PSI? For reference, I've had the gauge replaced 3 times.. behavior was the same on the previous ones.