backflow pipe sucking air in filter mode

[jillybean213]

I have a solar heated saltwater pool with a de filter. I cleaned the pump this spring and started it up and it's blowing crazy air bubbles out the jets and my pool pilot won't generate chlorine, keeps putting out the "check flow" alarm cause there's so much air in the system. I've burped the system but it doesn't help. I thought the filter was clogged so I washed it another 2 times and that didn't solve it. If I put the valve on recirc the air goes away.

When I switch to backwash then back to filter, the system runs fine for about an hour then starts sucking air again. I replaced the spider gasket, had that lubed and that didn't fix it either. Which leads me to think backwashing gets enough water in the pipe to block airflow but after an hour water has dissipated enough to let air back in. Help! What else other than the spider gasket could it be?

 

[duraleigh]

If you are sucking air into the system, it is not coming from anything after the pump. It can only come from the pump to the skimmer basket.

Do you have enough water in the pool so the skimmer is not sucking air? Turn on the pump and then observe the water going into the skimmer.

 

[basod]

You may have ruled out your mechanical seal if there are no bubbles when running in recirc mode.
once you backwash stop pump turn to rinse for ~1min stop pump and turn back to filter. If you turn the selector valve with pump running you may have damaged the new spider gasket
Listen at the selector valve for popping/boiling sounds.
Check the suction strainer basket(I'm assuming it's clean) for bubbles they should clear up within a few minutes.