Backwash when the pressure says so, not the calendar.

Once a week is a guess. Use the pressure gauge.

DE filters clog up at different rates depending on how much junk is in the water. Backwash when the pressure reads 8–10 psi above your clean starting pressure. That might be every two weeks or every two days during spring bloom. The gauge doesn’t lie.

Waste time and water by backwashing on a schedule. Or clean when it actually needs it. Your call.