I have been dealing with this issue all season.
In both recirculate and filter, the flow in and out of the pool is lower than it should be. Low enough that one of the skimmer weirs will not push down all the way. Also slowly but surely small bubbles form in the pump basket, until it is a large air pocket. In waste or backwash, there is no issue. The flow is full and strong. Often to fully prime the pump I have to start in waste and then switch to filter.
I have done the following
- changed drain plugs on pump
- changed strainer gasket
- changed pump housing gasket
- checked impeller for debris
- blew all the lines to account for any debris in return
- changed O-rings on Jandy valves
- Checked heater for proper flow (by-pass valve was replaced)
I am usually pretty good with the pool, rarely calling a professional service company - at this point I'm at the end of my knowledge. The only thing I haven't done is to start digging.
20,000 gallon concrete in-ground pool with vinyl coating (aka, aqua bright)
Hayward super pump 1.5 hp.
Hayward 40sq ft. DE filter
Jandy propane heater.