Backwash when pressure rises, not on a schedule.

You don’t backwash on a schedule. The clock isn’t the enemy — the pressure gauge is.

For a DE filter, you backwash when the pressure gauge reads 8-10 PSI higher than when the filter was clean. In heavy swimming season, that might mean every 2-3 weeks. Or it might be every week if you’ve got a party pool full of sunscreen and grass clippings. Could also be 4 weeks if you’re low-use. The number isn’t the point — the delta is.

Ignore the “backwash every 30 days” advice. That’s for people who don’t check their gauges. If you live on a timer, you’ll either waste water or let the filter choke. Watch the gauge, not the calendar.

Your filter doesn’t care what day it is.