Thanks for the feedback... really appreciate it.

Yes, the pressure gauge reads zero when off, and goes to same value each time it's turned on, so it seems the gauge is okay.

I did a bit of brushing the two days before backwashing, which was some combination of sand and/or algae, and I definitely saw that coming out of the backwash hose.

I'll take the filter apart and take a look in the near future...

hikernut