air in sand filter

hi ,I had a new intellflo vs in stalled last week it worked fine until monday night, I went to check on it monday night about ten and it wasnt pumping a lot of water looked for a blockage done thought the valves might of got moved nope, finally check the sand filter and it had a lot of air in it as the air escaped the pump started moving more water finally back to normal and ran ok all night, I was running the pump at 3050 rpm to clean and 1850 to heat the pool it was in the heat cycle that i had the trouble I turned the rpms up to 2,000 so we will see tonight it was fine all last night after turning the rpm's up any ideas ?

There's almost certainly a loose fitting somewhere. It could be the multivalve isn't seated and tightened down properly, or a fitting into the filter isn't tight, or a pipe is cracked. Air's being sucked in.

thanks for the info, the problem seems to have been in the pump lid, I put some water proof lube on the rubber gasket and that and cured the problem...