My pump pressure is fine if I have it set to circulate but if I turn it to filter my pressure rises to 20. I put new sand in it this year thinking that was the problem, it didn't help. It's a crystal flo 2 filter.
Ok, I will buy the testing kit this weekend and post the results.If flow is good right after backwashing and then it decreases after a short period of time, most likely you are filtering out something and usually it is algae. Post a full set of test results and also perform a OCLT (see pool school).