I have a Pentair Clean & Clear 420 Cartridge filter being pushed by a WhisperFlow 2 speed pump. For the life of me I can't remember what the startup pressure was when we first went live. I thought it was 12 PSI in high but it might have been in the low speed when the BP first started it up. I just replaced the cartridges with new ones and did not see a dramatic drop in PSI. Went from about 22 PSI with old cartridges down to about 18 PSI. Just trying to determine if I have something else going on. Flow on the return side seems OK. The filter is rated for 50 PSI max and I run a pressure side cleaner with no booster pump. Is 50 Max a realistic pressure to be hit? Seems high, even for a maximum.