Please Help...Pool not circulating

Jump to latest Follow Reply
Thomas45 said:
The water will flow, although it doesn't seem to flow at a high rate like when the top is off the MPV. One thing the video doesn't capture is after a few minutes, the pump will stop pulling/sucking water from the pool inlet pipe and start appear to cavitate. There is a video of the pump reservoir....
Click to expand...
You keep using the word cavitate but what I see in the video is definitely not cavitation.

Cavitation is basically the boiling of water. In a pool pump, if the pressure near the impeller drops below the vapor pressure of water, about 1 PSI above a perfect vacuum. the water vaporizes and then as it travels through the impeller, pressure rises and the vapor bubbles collapse making a popping noise. In order for this occur, the plumbing would need to cause a lot of head loss and that requires higher flow rates and no air in the system as air is both expandable and compressible. So it is nearly impossible for a pump to have cavitation if air is traveling through the impeller. Also, the cavitation occurs in the impeller and vapor bubbles do not rise in the pump basket, they travel out toward the pressure side of the pump. So I see no signs of cavitation in that video.

I think your issue is that the pump is not priming and you can hear the pump speed increase as time goes on as it tries to prime. When there is that much air in the pump basket, it usually points to one of several different problems:

- Pool Level is too low. It should be half way up the skimmer opening.

- Pump lid and/or drain plug gaskets are leaking in air. Need to be lubed.

- Impeller has a clog that needs to be removed.

- Suction line and/or other valves/unions are leaking in air.

- Something got stuck in the suction line.

- The suction line collapsed.
 
Last edited:
  • Like
Reactions: Jimrahbe
mas985 said:
You keep using the word cavitate but what I see in the video is definitely not cavitation.

Cavitation is basically the boiling of water. In a pool pump, if the pressure near the impeller drops below the vapor pressure of water, about 1 PSI above a perfect vacuum. the water vaporizes and then as it travels through the impeller, pressure rises and the vapor bubbles collapse making a popping noise. In order for this occur, the plumbing would need to cause a lot of head loss and that requires higher flow rates and no air in the system as air is both expandable and compressible. So it is nearly impossible for a pump to have cavitation if air is traveling through the impeller. Also, the cavitation occurs in the impeller and vapor bubbles do not rise in the pump basket, they travel out toward the pressure side of the pump. So I see no signs of cavitation in that video.

I think your issue is that the pump is not priming and you can hear the pump speed increase as time goes on as it tries to prime. When there is that much air in the pump basket, it usually points to one of several different problems:

- Pool Level is too low. It should be half way up the skimmer opening.

- Pump lid and/or drain plug gaskets are leaking in air. Need to be lubed.

- Impeller has a clog that needs to be removed.

- Suction line and/or other valves/unions are leaking in air.

- Something got stuck in the suction line.

- The suction line collapsed.
Click to expand...
mas985 said:
You keep using the word cavitate but what I see in the video is definitely not cavitation.

Cavitation is basically the boiling of water. In a pool pump, if the pressure near the impeller drops below the vapor pressure of water, about 1 PSI above a perfect vacuum. the water vaporizes and then as it travels through the impeller, pressure rises and the vapor bubbles collapse making a popping noise. In order for this occur, the plumbing would need to cause a lot of head loss and that requires higher flow rates and no air in the system as air is both expandable and compressible. So it is nearly impossible for a pump to have cavitation if air is traveling through the impeller. Also, the cavitation occurs in the impeller and vapor bubbles do not rise in the pump basket, they travel out toward the pressure side of the pump. So I see no signs of cavitation in that video.

I think your issue is that the pump is not priming and you can hear the pump speed increase as time goes on as it tries to prime. When there is that much air in the pump basket, it usually points to one of several different problems:

- Pool Level is too low. It should be half way up the skimmer opening.

- Pump lid and/or drain plug gaskets are leaking in air. Need to be lubed.

- Impeller has a clog that needs to be removed.

- Suction line and/or other valves/unions are leaking in air.

- Something got stuck in the suction line.

- The suction line collapsed.
Click to expand...
Thanks for the clarification on what cavitation is and is not. I agree about not priming and now that you mentioned it, I did notice before this issue started I would see the occasional air bubbling into the pool when it was first started.

The pool level is half-way up the skimmer and the basket is clean. I've already made sure the impellers are free and clear.

I have not lubed any of the gaskets, but will when I arrive back home on Sunday. One thing I did notice recently is there a small water leak (very small water drip) around the base where the MVP and the sand filter attaches when the pump first starts up.

Knowing how detailed I am about keeping both debris baskets clean, and on the water flows coming from the pool inlet line to the pump when it does work, I doubt I have a line blockage. But based on what I have learned so far, I will go buy a water blaster and connect it to the line just to make sure.

So how would I go about checking for air leaks, or if there is an issue with the suction line?

Finally, thank you all for the great advice and help.
 
Last edited:
  • Like
Reactions: mas985
Thomas, you have a fairly simple set up there, so diagnosing a potential suction side air leak should be somewhat straight-forward.. Maybe I missed it earlier in this thread, but be sure to check the following if you haven't done so already:
1 - Pump lid O-ring and drain plug(s) well lubed and not damaged.
2 - The union fitting connected to the inlet of the pump, check the O-ring inside to ensure it's lubed well and not pinched or out of its groove.
3 - Weir door at the skimmer not getting stuck closed on occasion.

It may not seem like much, but I don't think you ever posted a full set of water test results. If your filter is jammed-up with crud or organics, it can really effect water flow. We would still like to see a full set of water test results from your TF-100, TF-Pro, or Taylor K-2006C test kit.
 
  • Like
Reactions: mas985
Texas Splash said:
Thomas, you have a fairly simple set up there, so diagnosing a potential suction side air leak should be somewhat straight-forward.. Maybe I missed it earlier in this thread, but be sure to check the following if you haven't done so already:
1 - Pump lid O-ring and drain plug(s) well lubed and not damaged.
2 - The union fitting connected to the inlet of the pump, check the O-ring inside to ensure it's lubed well and not pinched or out of its groove.
3 - Weir door at the skimmer not getting stuck closed on occasion.

It may not seem like much, but I don't think you ever posted a full set of water test results. If your filter is jammed-up with crud or organics, it can really effect water flow. We would still like to see a full set of water test results from your TF-100, TF-Pro, or Taylor K-2006C test kit.
Click to expand...

I will check all the O-rings when I get home on Sunday and follow up with what I find. I have some silicon lube that I use on the dive gear O-rings, will this work to lube the pool O-rings as well?

The pool skimmer door is not stuck and functioning properly.....There is plenty of water in the skimmer

I will also update my signature when I get home, I don't have the pool measurements..
 
To me, it looks like the skimmer is running dry.

It is either that or you have some sort of obstruction in the suction line.

You can install a vacuum gauge in the front drain plug port to see what happens with the suction.

If the line is obstructed, then the vacuum will be high when the water stops flowing.

Be careful not to overtighten the vacuum gauge as it can crack the drain port.
 

Enjoying this content?

Support TFP with a donation.

Give Support
I would like to thank everyone for their help and advice due to the issue is no more. The pump is running strong with no issues except for the greenish color of the pool water due to not have the pump on in almost 5 days. I am not sure what it was so to "hopefully" help the next guy, this is what I did...
1. Bought a water blaster for 1.5 to 3 " pipes and ran it from the pump back to the skimmer. *I did not see an debris in the skimmer that would show a blockage.
2. Replaced the gasket under the MVP. Mine was glued it and a pain to removed. However, I was able to accomplish the task of removing the old gasket by using a razor blade and hot knife.
3. I disconnected all the screw joints and applied silicone grease the gasket and applied a light coat to the MVP gasket as well.
 
  • Like
Reactions: wireform, JamesW and Texas Splash
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply