Air flowing back through filter and displacing water from pot after shutoff

mentaimotse

Bronze Supporter
Apr 24, 2021
12
Summerville, SC
So I just got the hard plumbing in on my semi-agp (about 50% buried), and I'm having an issue where my pot partially drains after cutting the pump off. It sounds like air is bubbling back through the filter and pushing water out of the pump pot.

Perhaps related - despite starting and running the pump with the cartridge manual relief valve in both open and closed positions, I have never seen any water coming out of the relief valve.

I figured a video might capture what is happening better, and you can see it here - could the water not be exiting the manual relief valve because the cartridge is partially above the water level? Also, would a check valve between filter and pump solve the problem of air from the filter displacing water in the pot after cutoff?

In case it's helpful - the system was previously connected with the stock hoses and behaved in exactly the same way.
 

HermanTX

Gold Supporter
May 20, 2020
2,650
Katy TX
Pool Size
14600
Surface
Plaster
Chlorine
Liquid Chlorine
I noticed in your video that you were turning the top nut on the relief valve. While that should see pressure, but the relief valve opens by gripping the large diameter of that valve and turning it counterclockwise a quarter turn to relieve air from your system. It works on a pin in a slot that limits the rotation. A large port opens to bleed air. That top nut is a place for your air pressure gauge. See picture of the top half of the valve.

Air Relief Valve - top half with gauge.jpg

A check valve is best placed before the pump (suction side) to keep water in the pump basket.
 
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Poolbreh

In The Industry
Jul 31, 2021
272
San Diego
Very cool System brotha and nice video, the first things I’ve noticed is the pump basket seems to be in backwards. The opening of basket needs to be aligned with intake of pump. Like Herman pointed out above the part you are twisting to release air is for a pressure gauge. By twisting the whole cylindrical piece counter clockwise will release out of the 1/2” nozzle. It sounds and looks like the pump is starving or cavitation, , which is causing blowback. Do you only have a basket in the skimmer? Did you have to use a reducer bushing for the skimmer?(2-1.5”)
 
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mentaimotse

Bronze Supporter
Apr 24, 2021
12
Summerville, SC
I noticed in your video that you were turning the top nut on the relief valve. While that should see pressure, but the relief valve opens by gripping the large diameter of that valve and turning it counterclockwise a quarter turn to relieve air from your system. It works on a pin in a slot that limits the rotation. A large port opens to bleed air. That top nut is a place for your air pressure gauge. See picture of the top half of the valve.

View attachment 366826

A check valve is best placed before the pump (suction side) to keep water in the pump basket.
Thanks so much for this reply, although now I feel like an idiot for not using the relief valve properly. I've tightened the top nut all the way down and that may have been part of the issue, as I didn't see air pushing back into the pump after turning it off. I'm still getting a fair amount of blowback pushing the skimmer basket up but I'm wondering if that could just be due to the water velocity as the pump is so oversized.
 

mentaimotse

Bronze Supporter
Apr 24, 2021
12
Summerville, SC
Very cool System brotha and nice video, the first things I’ve noticed is the pump basket seems to be in backwards. The opening of basket needs to be aligned with intake of pump. Like Herman pointed out above the part you are twisting to release air is for a pressure gauge. By twisting the whole cylindrical piece counter clockwise will release out of the 1/2” nozzle. It sounds and looks like the pump is starving or cavitation, , which is causing blowback. Do you only have a basket in the skimmer? Did you have to use a reducer bushing for the skimmer?(2-1.5”)
Thanks for the reply Poolbreh, I will go out and fix the pump basket as soon as I'm home from work! The skimmer just has a basket and doesn't use any reducer fittings.
 

mentaimotse

Bronze Supporter
Apr 24, 2021
12
Summerville, SC
I noticed in your video that you were turning the top nut on the relief valve. While that should see pressure, but the relief valve opens by gripping the large diameter of that valve and turning it counterclockwise a quarter turn to relieve air from your system. It works on a pin in a slot that limits the rotation. A large port opens to bleed air. That top nut is a place for your air pressure gauge. See picture of the top half of the valve.

View attachment 366826

A check valve is best placed before the pump (suction side) to keep water in the pump basket.
Thanks Herman, I opened the valve (the right way) and released a lot of built up air in the filter; this seems to have fixed the issue with air in the system!
 

HermanTX

Gold Supporter
May 20, 2020
2,650
Katy TX
Pool Size
14600
Surface
Plaster
Chlorine
Liquid Chlorine
Thanks Herman, I opened the valve (the right way) and released a lot of built up air in the filter; this seems to have fixed the issue with air in the system!
well hopefully with that and also if you turned the pump basket to fit OK, the top of the pump basket may seal better and reduce any air being sucked in.

If you still have issues with flow back and priming, then you may need to consider a check valve a foot or more in front (on the suction side) of the pump. This will keep water in the pump when it shuts off.
 
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