i pull out one grid at a time...spray it and reinstall in the exact same spot.

By waste...i figure you mean backwash...it seem like it backwash OK...I can see dirt floating thru the clear glass. My backwash go directly to city sewer..so i can't see how much flow.

what i dont get is that....
when i turn on the booster pump to the polaris...i see no water at the return lines....with booster pump off...i see some water returns....