Happy Memorial day!
I've researched a bit and didn't see anything that quite answered my question.
After 4 days or so of runtime, the pressure on my sand filter drops from 20 psi to about 15. I clean the baskets daily (including the pump basket ) and it doesn't seem to help. However, after a backwash the pressure returns to 20. Could it be a bad guage? I used to work in an air force metrology lab and guages would surely fail... but in this case the repeatability of my symptoms doesn't seem to jive with a bad guage.
Thoughts are appreciated!