Bubbles in return - is this a problem?

Enumjon

Well-known member
Apr 30, 2020
102
Tijeras, NM
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi all,

My old single speed pump died, so I have been adjusting to a new VS pump over the past few weeks. I have noticed a massive amount of bubbling coming from a single return - the one on the far side of the pool from the equipment pad. Researching this site and a little experimenting is leading me to believe that the bubbles are coming from 2 sources.
1) VSP at a lower speed makes bubbles. Running RPM in the 2000's there is a big bubble in the pump - about 3-4 4 inches deep. When I turn it up to full speed the bubble goes away.
2) The solar heater pressure valve is not fully engaged at lower RPM, so air is being sucked into the system. Going up to the panel with the pump running at low speed you can hear the air rushing in, and simply putting my hand around the valve reduces the sound.

Normally a bubbling return is a big pH problem. However, I have a chronic high TA problem. It is strange, my pH is very stable at about 7.2-7.4, but my TA keeps rising (up to 190 now). It seems to me that the continually bubbling return should finally raise my pH, allowing me to add acid and reduce the TA. Is there a problem with this situation that I am missing, or is a bubbling return OK?
 

mas985

TFP Expert
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May 3, 2007
14,628
Pleasanton, CA
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#1 would not cause bubbles out of the returns. However, it does cause bubbles to accumulate in the pump basket.

#2 is the most likely cause of your problem. Higher speeds/pressure is necessary to keep the VRV closed. How high is the VRV in relation to the pump?
 

Enumjon

Well-known member
Apr 30, 2020
102
Tijeras, NM
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
#1 would not cause bubbles out of the returns. However, it does cause bubbles to accumulate in the pump basket.

#2 is the most likely cause of your problem. Higher speeds/pressure is necessary to keep the VRV closed. How high is the VRV in relation to the pump?
I would guess 15 feet above the pump.
 

mas985

TFP Expert
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May 3, 2007
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Pleasanton, CA
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For 15 feet, your filter pressure probably needs to be above 8 PSI to keep the VRV closed. What is the filter pressure now?
 

Enumjon

Well-known member
Apr 30, 2020
102
Tijeras, NM
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
For 15 feet, your filter pressure probably needs to be above 8 PSI to keep the VRV closed. What is the filter pressure now?
At work, so cannot tell for certain, but it was right about 8 psi. I can play with numbers to see what it takes to keep it closed. If the valve is open am I getting less water flow, and thus less heating?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,628
Pleasanton, CA
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Salt Water Generator
It depends on the plumbing setup and the head curve of the pump. Have you measured flow rate in any way or felt the panels? Warm panels usually indicates lower than optimal flow rate. You want at least 0.1 GPM/sq-ft of panels.
 

Enumjon

Well-known member
Apr 30, 2020
102
Tijeras, NM
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
Warm panels means not enough flow - I love that sensible response. Unfortunately it was cloudy and windy last night, and is supposed to be the same tonight, so the panels would be cool regardless. Won't be able to check until tomorrow to see if the flow is enough.
 
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