Pump loses prime after shutdown

[BearMare]

My pump loses prime quickly after shutting down. Once primed the pump if strong with no leaks visible on the pressure side. The pump sits 1’ above pool water level, DE filter with only one check valve after the pool heater. I’ve noticed when the pump is shut down, the filter starts to suck in air if you open the pressure valve resulting in the pump water level being suck up enough where the pump won’t prime by itself. If I disconnect the plumbing prior to entering the multi-port valve it doesn’t do this. If I take the lid off of the pump the water level is just below the pump inlet, if I open the pressure relief valve on top of the filter, water will fill up the pump basket and overflows. I can put the lid back and the pump starts without any problems. There is a lot of air built up in the filter that release when the pump starts. This problem started when I put new DE grids into the filter. I place a check valve between the pump outlet and multi-port valve, made problem worst as now I can’t take lid off the basket and open pressure valve to fill pump basket. After adding the check valve, I noticed a leak in the bottom of the seal plate which wasn’t there prior to installing the check valve. When I shut the pump down there is a lot of gurgling in the pump and filter tank while the water lowers in the basket (lid is still on) Also, there are no air bubbles coming out of any of the return jets going into the pool. I did have bubbles coming from one of the return jets a while back, but it went away after changing the O-ring in the automatic chlorinator!
I changed the spider gasket in multiport valve as well.

Any suggests will be greatly appreciated.

 

[Texas Splash]

Welcome to TFP! So you seem to have a few things happening at once, and these things may or may not really impact each other. For example:
- Replacing the chlorinator O-ring should've had no bearing on bubbles at the returns jets since it's on the pressure side.
- That check valve took away your potential to do a quick pump fill with the lid off. I do that all the time as well.
- The air gurgling when the system is off is a classic air leak; but it can be anywhere. It may not squirt water out, but will suck air in, so they can be tough to find.
- Start with the following if you haven't done so already:
** Pump basket clear lid o-ring in good condition and lubed. Pump drain plugs as well.
** Check the filter pressure gauge and/or air relief valve. They can let air in when bad. You might see a tiny o-ring there as well.
** You have several 3-way valves, and any of those could be letting air in. You may need to remove the top of each one, check the handle/stem o-ring and lube.
** Check the union fittings too.

If there is something wrong at the seal plate, that could be an problem. But I'd still start with the easy stuff above before anything else.

 

[BearMare]

Changed orings on all jandy valves, new orings seal plate, shaft sea and basket gasket. didn't do anything with the pressure gauge seal will replace next. Question, air is probably not induced into the pressure side of the system when the pump is running, but is it sucking in air when the pump is shut down?

 

[Jimrahbe]

Bear.

I have seen filter air relief valves letting air leak in, yet no water out. Often just cleaning them out fixes the problem. As does replacement of course.

When you turn the pump off, and you can hear air entering the filter, my first place to look is the air relief valve.

Thanks,

Jim R.