I'm baffled. My Hayward Superpump and MPV, when set to filter as brand new without adding DE showed a pressure of 10psi. So that's baseline with a water path impeded only by empty grid fabric. Adding DE brought the psi up to maybe 11 or 12. So that's a more useful baseline. Later, I was experiencing higher pressure AFTER backwash, 15 to 17; even after multiple backwash/rinse cycles and clear water, I couldn't get the pressure below 15 psi. So here's the weird part: I removed the filter grids from the filter and closed it up and turned it on. With nothing in the water path, just water coming into the empty filter case and exiting without passing through any media, I'd expect pressure to drop back to 10psi, or at least to drop lower than with installed grids. But STILL stuck at 15psi. There should be no difference now between recirculate and filter except a foot or two of extra travel for the water. Pressure gauge is a year old, fluid-filled, seems to move ok, does drop to zero during recirc or power off, does rise to 20 or so before I backwash. The filter has big inlet and outlet ports, there's no clog I can see. Pump basket is empty, no debris in the impeller and again, nice low pressure without the filter inline which means my pipes should be clear. The only piece that remains an unknown is the MPV, which I hear is tough to take apart and reassemble. Google only offers information about leaking MPVs and replacing gaskets, nothing about clogs. Anyone encountered this before? This problem appeared last year and I just lived with it.