New to Variable Speed Pumps; Air in Returns

[tonyc2000]

I am new to this forum and have enjoyed reading a number of threads about air bubbles in return jets. But, thought I would contribute my situation and see whether there is need for concern. After many years of single speed pump usage, I made the transition to the Pentair Intelliflo2 VSF. The installation was done by a large, national chain store and for the most part, I am pleased with the level of service and the redesigned plumbing. The installation included the pump and four Pentair diverter valves. (wish I would have specified Jandy..) I am getting accustomed to the broad range of operating parameters but, regardless of operating speed, I get tiny air bubbles coming from the pool/spa returns.

The bubbles are seen at various speeds I have tested: 100%, 70%, 50% and 35%. All indications point to a suction side leak. The installer came back and check a number of things but in the end said it probably is not a problem and to keep an eye on it. My biggest concern is the gurgling and chattering I hear in the pump. Is this normal for a VSF? Or, is it cavitation? The installers used a clear pipe glue which I had never seen before. After installation and startup, I found a few wads of glue residue in the pump basket and in the pool. Could the impeller be clogged ?

Other comments: I tried running the pump at full speed; then, turning it off to detect spurts of water from suction side of plumbing. Nothing there.
I also notice quite a bit of gurgling on the return fitting coming out of my ancient heater. The inline chlorinator has a one way check valve that is quite old and wondering whether it could be the source of the problem.

Like other posts I've read, it is not unusual to see a fair amount of air in the pump basket; something I never experienced with a single speed. When the pump starts, it goes into priming mode and fills the basket. During that period (and a short period afterward) I see a very large amount of air come from the returns. Once the pump settles into normal mode (70% and then 50% later in the day), that's when i see continuous, tiny bubbles.

Thanks for reading. Hope to see some interesting responses and start learning about more ways to ENJOY ~!

 

[reggiehammond]

Not typical no. The only thing typical about VSP running low speed is the presence of a small air bubble forming at top of pump pot.

You have an air leak, that’s obvious. You shouldn’t hear cavitation at the pump, or noise anywhere, really.

I had good luck using a water hose to put a small stream of water on all fittings, unions, and drain plugs. Once you hit the right spot, the noise will disappear. Do you have any air in the pump pot during normal operation? Does the pump pot stay full on a fairly low speed?

What are your speeds and pump schedule you’re running now?

 

[1poolman1]

I am new to this forum and have enjoyed reading a number of threads about air bubbles in return jets. But, thought I would contribute my situation and see whether there is need for concern. After many years of single speed pump usage, I made the transition to the Pentair Intelliflo2 VSF. The installation was done by a large, national chain store and for the most part, I am pleased with the level of service and the redesigned plumbing. The installation included the pump and four Pentair diverter valves. (wish I would have specified Jandy..) I am getting accustomed to the broad range of operating parameters but, regardless of operating speed, I get tiny air bubbles coming from the pool/spa returns.

The bubbles are seen at various speeds I have tested: 100%, 70%, 50% and 35%. All indications point to a suction side leak. The installer came back and check a number of things but in the end said it probably is not a problem and to keep an eye on it. My biggest concern is the gurgling and chattering I hear in the pump. Is this normal for a VSF? Or, is it cavitation? The installers used a clear pipe glue which I had never seen before. After installation and startup, I found a few wads of glue residue in the pump basket and in the pool. Could the impeller be clogged ?

Other comments: I tried running the pump at full speed; then, turning it off to detect spurts of water from suction side of plumbing. Nothing there.
I also notice quite a bit of gurgling on the return fitting coming out of my ancient heater. The inline chlorinator has a one way check valve that is quite old and wondering whether it could be the source of the problem.

Like other posts I've read, it is not unusual to see a fair amount of air in the pump basket; something I never experienced with a single speed. When the pump starts, it goes into priming mode and fills the basket. During that period (and a short period afterward) I see a very large amount of air come from the returns. Once the pump settles into normal mode (70% and then 50% later in the day), that's when i see continuous, tiny bubbles.

Thanks for reading. Hope to see some interesting responses and start learning about more ways to ENJOY ~!

Cavitation is very noisy, like rocks in the pump. Inline chlorinator is on the pressure side (and should not be used) so it would be a water leak, not air. Does sound like a minor suction leak, perhaps at the inlet port. Was a union used?

 

[tonyc2000]

Not typical no. The only thing typical about VSP running low speed is the presence of a small air bubble forming at top of pump pot.

You have an air leak, that’s obvious. You shouldn’t hear cavitation at the pump, or noise anywhere, really.

I had good luck using a water hose to put a small stream of water on all fittings, unions, and drain plugs. Once you hit the right spot, the noise will disappear. Do you have any air in the pump pot during normal operation? Does the pump pot stay full on a fairly low speed?

What are your speeds and pump schedule you’re running now?

The slower the speed, the more air seen in the pot. From 9am to 11am, it runs at 70% speed. From 11am to 4pm, it runs at 50%. The auto priming occurs before the first schedule. As the prime completes, that's when is see a ton of air coming from the returns. After that it settles down to tiny bubbles. At 70% there is a considerable amount of air swirling in the pot. At 50%, the water level in the pot goes down and not near as much 'swirling'. Thanks for your help!

 

[tonyc2000]

Cavitation is very noisy, like rocks in the pump. Inline chlorinator is on the pressure side (and should not be used) so it would be a water leak, not air. Does sound like a minor suction leak, perhaps at the inlet port. Was a union used?

@1poolman1 The noise I hear sounds like pebbles rolling around. After using my home made stethoscope, this noise may be coming from the check valve located between near the inline chlorinator. This is especially noticeable at the 50% speed. I definitely agree with you suspicion of minor leak on the suction side but, darned if I can find it. Seems like the installer should, however. For what I paid, I want this system to work correctly.
When you say "should not be used", are you referring to the inline chlorinator itself or the check valve located next to it?

 

[1poolman1]

@1poolman1 The noise I hear sounds like pebbles rolling around. After using my home made stethoscope, this noise may be coming from the check valve located between near the inline chlorinator. This is especially noticeable at the 50% speed. I definitely agree with you suspicion of minor leak on the suction side but, darned if I can find it. Seems like the installer should, however. For what I paid, I want this system to work correctly.
When you say "should not be used", are you referring to the inline chlorinator itself or the check valve located next to it?

Inline and off-line tab feeders are a source of a lot of damage to residential pool equipment. Whatever check valve you have, even the ones made by Pentair (Rainbow) as chemical -resistant will fail and the damage will be done before you notice it. They were designed for use on commercial pools, many having their equipment running 24/7.

 

[reggiehammond]

The slower the speed, the more air seen in the pot. From 9am to 11am, it runs at 70% speed. From 11am to 4pm, it runs at 50%. The auto priming occurs before the first schedule. As the prime completes, that's when is see a ton of air coming from the returns. After that it settles down to tiny bubbles. At 70% there is a considerable amount of air swirling in the pot. At 50%, the water level in the pot goes down and not near as much 'swirling'. Thanks for your help!

I think if you put pump on full speed, the problem gets worse. Use a steady stream for a water hose on all of the different fittings, unions, check valves, etc. Once you find the source of leak, the pump pot should instantly fill with water confirming the leak. It’s actually fairly easy process, especially since you already suspect the check valve.

Once you solve the air leak - I’d encourage you to work on pump speeds. There’s not typically any reason to run your pump as hard as your schedule does… it’s just burning electricity and money, for very little practical effect.

 

[tonyc2000]

Thanks to all for your comments. For a couple weeks, I have been performing various combinations of running parameters in order to find the suction side air leak. On one occasion, I found the following behavior:

Running pump at 70% with the diverter valve at about 60% skimmer/40% main drain. (This is a rough estimate for illustration only). If I slightly increase the skimmer flow to roughly 75%, I begin to hear gurgling in the valve and observe an increase of air in the pump basket. Then, small bubbles of air in the pool returns. What's interesting is that if I go beyond 75% (say, 85%), the observed air begins to diminish. The diverter valve is a Pentair 3-way.

Prior to this installation, I was only familiar with Jandy valves which served me well for 25 years. Are Pentair valves good quality? Could the Pentair valve itself be the source of my problem? Or, does this behavior simply indicate a bad glue connection on the skimmer side of the valve?

 

[tonyc2000]

An update on my issue of air in the returns: I was continuing a struggle with balancing speed and diverter settings in order to minimize air in returns. Never quite getting it right. One day, I detected the sound of air near the 2 1/2" to 2" reducing bushing near suction inlet. Also noticed a 3/8" gap between the bushing and the pump union. In my experience, bushings are typically flush against the coupling or union. To test for a suction leak, I applied a coat of shaving cream to the joint. Well, that must have been just enough lubrication for the bushing to slam into place. After shutting down, I tapped the joint with a rubber mallet and it began to come apart. Bottom line: the installer forgot to glue the bushing into place. After gluing the bushing, air in returns appears to be resolved.

At 70% speed, the strainer pot is now completely full of water. What continues to surprise me is that at 35% speed, the water level in the pot goes down about 3/4". This is far better than before the fix......at slow speed the water level was at the suction inlet. But, I still scratch my head on why the the water level in the pot would go down at all on slower speeds. Of course, when the pump primes on the next day, the pot fills completely again. So, not really a problem that I am concerned about. All is good !