Also posted on Home Improvement forum. Looking for any help I can get.

I just cleaned the grids on my Hayward DE filter. Started everything back up and the pump starts to cavitate and the filter housing fills up with air. I've bled the air off for days but it continues to gas up. This same thing happened the last time I cleaned them but never before. I'll describe my troubleshooting below but the last time I gave up and shut the pump off for 4 or 5 days before the pool tech could get here to diagnose. When he arrived we started the pump, bled some air off, and everything ran perfectly fine.

During my first round of troubleshooting I replaced the union on the suction side of the pump. I replaced the pump lid and gasket. I can run water over all the suction piping and the bubbles don't stop. I replaced the gasket on the valve on the suction that differentiates between either the pool or the spa. None of that helped. It was not until what I described above happened before everything worked right again.

I'm back in the same boat and have no idea what fixed it the last time, so I have no idea what to do this time. I'm in south east Texas so can't afford to leave the pump down for days without building algae, which means I'll have to open up and clean the grids again after filtering all the algae.

Anyone have any thoughts or ideas?

Thanks.

Its been a while since i have messed with a residential pool filter. So I have a couple of thoughts.

Assuming there are no leaks downstream that you are not aware of:

Maybe the purge valve went bad and is not closing all the way shut (or seal at pressure gauge or the entire cap assembly everything screws into). Purge valves are cheap and need to be swapped out occasionally. they may have them on the shelf at Leslie.

The cap assembly and or the other parts that screw in may need new gaskets and O-rings with a little silicone grease. Not 100%sure if the gauge and valve have gaskets, but I think the cap assembly has an O-ring.

You may have to give it a bit of a backflush to force the issue after you have checked O-rings - seals - valves etc.

My neighbor had basically the same problem last year. We could not get the air out of the system, and the pump just cavitated. It ended up being a cracked cap/lid on the suction strainer that we couldn't see. swapped it out with one from another pump, and voila!

Koko Chingo said:

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The cap assembly and or the other parts that screw in may need new gaskets and O-rings with a little silicone grease. Not 100%sure if the gauge and valve have gaskets, but I think the cap assembly has an O-ring.

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This was our problem when we'd get air in the system. The cap with the handle you use to turn from backflush, circulate, etc had a gasket that would tear insanely easy any time you turned the handle. We replaced the gasket probably 5 times before we ended up replacing the entire assembly. Haven't had the issue since we did that.

I think you need to prime the pump by putting the hose down the hole on the pool side of the lint basket to fill that line back up with water (the intake line). After your convinced its full quickly screw the lint basket cap/top back on and start the pump. Be sure to vent the gauge on top until water gushes out...then close it.

Give that a shot.

Sounds like a suction leak. Put shaving cream on connections and fittings. Leak will stop if you cover it.

O ring on the intake pipe inside the filter assembly?

I'm with cowtown. Prime the pump.

Shaving cream test is always a good way to check for leaks in systems under vacuum. You will see the shaving cream getting sucked into the crack. But small leaks like that typically don't starve a pump. But it is a quick and easy check.

Underground leaks can certainly happen but again, typically don't starve the pump.

That's interesting. I haven't really messed with anything on the discharge side of the pump, thinking that should all be positive pressure on that side. Wouldn't any air drawn in there just end up in the pool and not back to the pump?

I'll give this a shot. Thanks.

Start at the skimmer. Are you pulling in air anywhere poolside? Suction side vacuum hose? Weir gate sticking? Didn't see you mention these in the OP. 90% of the time we diagnose air leaks it's not at the equipment.

fire09 said:

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Start at the skimmer. Are you pulling in air anywhere poolside? Suction side vacuum hose? Weir gate sticking? Didn't see you mention these in the OP. 90% of the time we diagnose air leaks it's not at the equipment.

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Pool level is good. Suction skimmers are clean and don't seem to be drawing in air. Weir gate sticking as in remaining closed? So it's drawing in air? I'd say if anything they may be stuck open. I have a booster pump for the vacuum that I've done similar checks on. Running water over piping, plugs are in tight and secure.

If you have a booster pump then you have a positive pressure vac. Weir gates can stick closed (vertical) but a quick look in the skimmer and you would know you are pulling in air. Next culprits are usually loose couplings at the inlet, cracked lid, bad o-ring on lid. Sounds like you already checked a bunch of that.