Air bubble when main drain valve closed

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shiyang100

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Jun 11, 2016
153
Boston, MA
I am having some imbalanced skimmer issues. So I played with vavles these days. I have three vavles in front of pump, one for main drain, two for skimmers.

Once i I close main drain vavle, there will be some consitent air bubbles. Once it is open, no more air bubbles. Why this happens?

another question, I have system 3 filter. I was told by PB that I don' t need to open air bleed vavle on the top to remove the air since there is an air bleed tubing inside. However, every time when I clean the pump basket, I have to open the air bleed vavle to get rid of air. Otherwise they will just stay there. I tried once, it stays there for 2 days, once I open air bleed vavle, it is gone. What this indicates? A blocked air bleed tube?

thanks so much.

happy 4th of July.
 
It is probably an air leak. When you close the MD valve, the suction in the pump basket increases making an air leak more likely. Lube the pump lid gasket and drain plugs with pool lube.

How much does the filter pressure change with the MD on vs off?

Regarding the air tube, sometimes they do get block but also, they don't go to the top of the filter either so there is always some air they cannot purge.
 
Yes. If the water level is too low, air can enter the skimmer.

Besides that, the only other way would be a leaky pipe or valve.
 
Thanks. I will check in the morning.

in term of air bleed tube, I guess I didn't ask my question clearly. Every time I cleaned the pump basket, there would be some air left under the lid. I can get rid of air by open air bleed valve connected with pressure gauge. But my PB always told me the internal air bleed tube should take care of this, and I should never open air bleed valve. But in fact, if I do not open air bleed valve, the air will stay under pump lid forever. Is there anything wrong here?
 

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Spent some time today. When the main drain valve closes, there will be some air bubbles. Closing other two skimmer valves does not increase the air bubbles.

However, I did notice there are some tiny bubbles circulating under pump lid. It is about a quarter size air bubble on the top when I turn off the pump. I did not have these problems before. Checked the o-ring and used some magic lube. Also checked drain plug and put magic lube on the o-ring as well. No improvement. Did running water test, couldn't tell the difference. What should I do next?
 
The only other thing I can think of is the valves. Maybe one of them is leaking. My guess is the MD valve since that is the one that you are moving.
 
What kind of valve is it? Can you remove the top of the valve to inspect the o-rings?

Another possibility is any unions that might be on the suction side of the pump.
 
Hey, sometimes when a valve isn't moved frequently that shafts orings on the diverted will dry up on one side causING an air leak when you turn the valve. Best way to diagnose this is to turn the pump off while it was running and immediately water will spit out on the suction side showing where you're getting your air leak from.

Make sure you test each valve separately.
 

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