Your filter probably needs a deep clean.

Most likely, the filter media is fouled with oils, sunscreen, algae residue, or dissolved metals that a simple backwash can’t touch. The pressure spikes again fast because the debris is still in there — just re-distributed.

For sand filters, the sand can get “channeled” or coated. You need to bust out a degreaser like a filter cleaner or even dishwasher detergent (check your manual). Let it soak overnight, then backwash again.

Cartridge filters are simpler but sneakier: the pleats trap fine particles that don’t rinse off with a hose. Soak them in a chemical cleaner, or just replace them if they’re overdue.

DE filters are the worst about this. The grids can get caked with calcium or oil, and backwashing barely touches it. You’ll have to take the grids out, soak them in acid or a degreaser, and scrub gently.

Also worth checking: your multiport valve gasket could be leaking water back into the waste line, causing false high pressure readings. But nine times out of ten it’s just a gunky filter.

Don’t keep backwashing repeatedly — that’s like rinsing a dirty dish with cold water. You need soap.