Tom wrote:
Several years ago we replaced the pump on an in ground pool with a DE
filter. The new pump does flow more water and things were fine for
the first season and then pressures would go up, output would
decrease and the pool would get green. The DE would get changed with
a grid cleaning and things were OK for a mounth or so then green
pool. The grids were changed as we noticed DE in the bottom of the
pool. Now we are back to high pressures, low flow, air on the
suction side (the leaf trap on the pump has an air pocket), geen
pool. The pump is just barely below the water level in the pool. Did I get
sold a pump that is to big? It is a Whisper Flow 3/4 hp
with 1&1/2 inch piping. Tom

If the pressure starts rising, doesn't that indicate that the filter is plugging
up? I thought that when that happens with DE, you were supposed to reverse flush
the filter, then add new DE to the intake to re-coat the filter. I haven't had
a DE filter in 20 years, so I'm no expert.

A little bubble in the trap is probably not a big problem. If there's
continuous air coming in, you have an intake leak which should be fixed. The
pressure going up would reduce the flow into the intake and lessen the air
problem, so the filter plugging up is probably not increasing the air problem.