Air bubbles in suction side check valve

[poscicapo]

Hello,

I have a spill over basin with a drain at the bottom of it that utilizes a single 2” pipe that runs about 125 feet (mostly uphill) to a pump that returns water to the main pool.

I have been in this home 8 years and it has always worked flawlessly.

A couple of months ago, I noticed an issue where the pump would prime maybe 75% and then draw down and try to prime again, etc. It gradually came to a point where it primes about 5% of what it should. It looks like someone is pouring a cup water into the basket and the motor just grinds away loudly and constantly. I quit using it when they happened in order to not burn up anything.

When I look at the check valve in the attached picture when the pump is running, there are a significant amount of bubbles coming up alluding to a suction side leak. Yes, I know the valve is installed sideways in the picture… The check valve is good and I have swapped out two different ones to be sure.

Anyway, I had a trusted leak detection company come out that had already identified and fixed a leak in the main pool about a year ago. The same guys come out and pressurize the line and tell me that it is holding pressure.

I am at a loss. They suggest I replace the ball valve after the check valve (orange handle in picture) and see if that corrects the problem, even though bubbles are clearly coming up from the bottom of the window in the check valve. Fine…I replaced it, and it did not fix the issue. Also, the motor is new and 3HP, it has a new shaft seal, new impeller, and new lid with new seal.

Is it possible a suction side line holds pressure for a leak detection test and the cracked pipe or bad joint somewhere only pulls air when the system is pressured and sucking from the motor?

The leak detection company really seems to have no solution. Basically they just said the line held pressure and said they timed it and watched their gauge and it didn’t budge.

What do I do to fix it? Dig up the entire line? Is there any other way to test the line and locate the leak?

Thank you for any suggestions or ideas you may have.

 

[Texas Splash]

Welcome to TFP! While you have a valid concern about a potential suction side leak, your early comment about the grinding sound at the pump makes me concerned about a potential cavitation scenario. For that I'd like to tag @mas985 for another opinion.

As to the suction line itself, if they saw no loss of pressure from point A to point B (plug-to-pressure device), then that portion of the line should be fine. Anything outside of the plug and pressure spot are suspect. Silly question but I have to ask .... with that new pump, the lid O-ring and drain plugs are lubed well correct?

But let's give Mark a chance to see your thread to see what he thinks.

 

[mas985]

Hello,

I have a spill over basin with a drain at the bottom of it that utilizes a single 2” pipe that runs about 125 feet (mostly uphill) to a pump that returns water to the main pool.

How much higher is the pump than the water level in the basin?

Thank you for any suggestions or ideas you may have.

While the pump is running, have you checked the basin to make sure that the water level is high enough such that there is not a vortex being created at the drain which is sucking in air?

Have you made sure the impeller is clear and free from debris? Check the inlet first and you may need to pull the wet end off the motor for a more thorough check.

 

[Nashman]

Welcome to TFP! While you have a valid concern about a potential suction side leak, your early comment about the grinding sound at the pump makes me concerned about a potential cavitation scenario. For that I'd like to tag @mas985 for another opinion.

As to the suction line itself, if they saw no loss of pressure from point A to point B (plug-to-pressure device), then that portion of the line should be fine. Anything outside of the plug and pressure spot are suspect. Silly question but I have to ask .... with that new pump, the lid O-ring and drain plugs are lubed well correct?

But let's give Mark a chance to see your thread to see what he thinks.

Thank you. Yes, everything has been lubed.

The owner of the pool company I used here (Optimal pools) came recommended and they are highly rated on google. He said he thought it was a leak in the pipe somewhere. It’s strange.

 

[Nashman]

How much higher is the pump than the water level in the basin?

The pump is about 20 feet higher. The basin is not losing water.

While the pump is running, have you checked the basin to make sure that the water level is high enough such that there is not a vortex being created at the drain which is sucking in air?

Yes. There is definitely not a vortex. The low suction at the floor drain is relative to what I would expect given the low volume of water being pulled into the pump basket. The basin is about 2 feet deep at the moment.

Have you made sure the impeller is clear and free from debris? Check the inlet first and you may need to pull the wet end off the motor for a more thorough check.

Yes. Impeller was replaced with the new shaft seal and motor. This is a Jandy/Zodiac pump. The motor is about a month old.

The pump housing itself according to leak detection and the pool company is fine. There are no water leaks/cracks.

When the motor starts, it pulls really hard like I am used to hearing when it worked.
I used a pool company recommended by leak detection of Mid TN called Optimal pools. They have 5 star google reviews and the owner seemed to agree the force of suction for start up sounds great. It just never primes completely.
The suction side pipe even flexes a little every few seconds with the force of the pull, but all we see is water with upward pulses of air bubbles in the check valve window. I can’t wrap my head around it being anything else. Would I see rising air bubbles in that check valve window if there is a leak in the plumbing anywhere after the check valve, like the pump housing itself or lid or back plate o-ring, etc.?

All of this is new (except the pump housing) anyway so it is mystifying.

Optimal pools said he thought I had a break.

Thanks again.

 

[Poolbreh]

125ft uphill is a long run. Unless there is another shut off by the basin, by changing the check valve that 125ft of pipe would have drained back into the basin. I cant imagine the pump being able to prime without some assistance.

 

[Nashman]

125ft uphill is a long run. Unless there is another shut off by the basin, by changing the check valve that 125ft of pipe would have drained back into the basin. I cant imagine the pump being able to prime without some assistance.

I have been here 8 years with no problems ever, so it’s extremely bizarre.
It has never taken more than about a dozen fills of water in the basket and start/stops for the pump to spin up and fully prime.
There is no cutoff valve between the floor drain to the pump. Pool company did blow out the line from the pump and all air came out of the floor drain.

 

[Poolbreh]

and it primed up easily after replacing the check valve?

 

[Divin Dave]

Is your filter clean? I had a similar experience that believe it or not turned out to be due to my filter being extremely dirty. Yes, shame on me. I cleaned the filters and the problem was solved.

To check to make sure all your above ground plumping and pump lid aren't leaking....
Get a water hose ready
Start the pump. Slowly pour water all over your pump lid, and all above ground plumbing. If there is a suction leak, this test will find it and you will know it. There will be no doubt.

Also, instead of a water hose, you can use Barbasol shaving cream to do the same test. If there is a suction leak, it will suck the shaving cream in.

 

[Nashman]

How much higher is the pump than the water level in the basin?


While the pump is running, have you checked the basin to make sure that the water level is high enough such that there is not a vortex being created at the drain which is sucking in air?

Have you made sure the impeller is clear and free from debris? Check the inlet first and you may need to pull the wet end off the motor for a more thorough check.

Could the pump housing itself be damaged somehow from previous dry running/cavitation? We had a lid seal go bad on this many months ago. I was out of town and my wife ended up starting the motor and getting distracted and not making sure the pump primed. It ran dry for several hours.
That was part of the reason I replaced everything originally, but the pump was still priming fine for a period of time after that happened. I was shocked that motor was still working, but the ink on the heat sensitive sticker on the motor faded away , so I thought I had better get a new one.

 

[mas985]

Could the pump housing itself be damaged somehow from previous dry running/cavitation?

Sure. It could have developed a crack or a warp in the pump lid allowing air into the pump basket. But that would not explain seeing air in the check valve.

What about the questions I asked?

 

[Nashman]

and it primed up easily after replacing the check valve?

Yes. It has not taken more than what has been normal at ~12 tries. It’s probably pulling ~15 gallons per minute if I had to guess.

 

[Nashman]

Sure. It could have developed a crack or a warp in the pump lid allowing air into the pump basket. But that would not explain seeing air in the check valve.

What about the questions I asked?

Yes. I answered above, and I can see my reply but it says under what I wrote that it is waiting for moderator approval.

 

[Nashman]

Is your filter clean? I had a similar experience that believe it or not turned out to be due to my filter being extremely dirty. Yes, shame on me. I cleaned the filters and the problem was solved.

To check to make sure all your above ground plumping and pump lid aren't leaking....
Get a water hose ready
Start the pump. Slowly pour water all over your pump lid, and all above ground plumbing. If there is a suction leak, this test will find it and you will know it. There will be no doubt.

Also, instead of a water hose, you can use Barbasol shaving cream to do the same test. If there is a suction leak, it will suck the shaving cream in.

There is not filter on this line. It simply pulls from the basin and returns to the main pool and the pool must filter that water. I probably should add one.

 

[mas985]

The pump is about 20 feet higher. The basin is not losing water.

That can't be right. At most, a residential pool pump will only lift water only about 8'.

 

[Nashman]

That can't be right. At most, a residential pool pump will only lift water only about 8'.

I just measured. It is around 12.6 feet. This is the bottom to the spill over ledge from main pool water line at 105 inches and another . From main pool water line to height of pool equipment pad

 

[Nashman]

That can't be right. At most, a residential pool pump will only lift water only about 8'.

I’m sorry, I meant to type before clicking reply. I measured and it is right around 12.5 feet. The bottom of the basin to the pool water line/spill over is about 105 inches. About another 4 feet from to equipment pad

 

[mas985]

The important elevation measure is from the basin water line to the inlet of the pump.

12.5 feet is still beyond any residential pool pump priming capability. If it is truly that high, you may need to fill the suction line manually or it will probably never prime.

At one time, that line may have been manually primed and the check valve keeps it primed. However, if the check valve was replaced, that line lost prime and needs to be manually primed again which is no easy feat.

Is there a valve near the drain in the basin? If so, close that valve, remove the check valve, fill the pipe through the check valve hole until it overflows. Reinstall the check valve. Then open the basin valve.

What is the model # of the pump you are using?

 

[Nashman]

The important elevation measure is from the basin water line to the inlet of the pump.

12.5 feet is still beyond any residential pool pump priming capability. If it is truly that high, you may need to fill the suction line manually or it will probably never prime.

At one time, that line may have been manually primed and the check valve keeps it primed. However, if the check valve was replaced, that line lost prime and needs to be manually primed again which is no easy feat.

Is there a valve near the drain in the basin? If so, close that valve, remove the check valve, fill the pipe through the check valve hole until it overflows. Reinstall the check valve. Then open the basin valve.

What is the model # of the pump you are using?

Ok. I would need to measure, but 8 feet would be pretty darn close at the water line assuming the basin is completely full. They measurement was taken from the bottom/drain level.

The thing is, I have regularly removed the check valve over the years to clear out leaves that have been stuck in it. I reinstall it and could always completely prime it with 10-12 tries.

The pump is a Jandy SHPF3.0

Unfortunately, there is not a check valve down there near/around the basin. I know the general direction the pipe runs to the pump per a recent conversation with the pool builder, but that is about it. Previous owners put in the pool.

 

[mas985]

The thing is, I have regularly removed the check valve over the years to clear out leaves that have been stuck in it. I reinstall it and could always completely prime it with 10-12 tries.

The pump is a Jandy SHPF3.0

That is a pretty large pump so it will prime at a little higher elevation. But you are probably still near the limits of the pump. Normally, you shouldn't need 10-12 tries to prime a pump. In a properly designed system, it should prime the first time.

Unfortunately, there is not a check valve down there near/around the basin. I know the general direction the pipe runs to the pump per a recent conversation with the pool builder, but that is about it. Previous owners put in the pool.

Not a check valve but a regular valve near the basin.

Try this:

1) Make sure the basin is close to 1/2 filled. It looks a little low in water which makes it that much harder to prime.
2) Close the manual valve right before the pump
3) Fill the pump basket with water until it overflows
4) Put the pump lid back on as tight as possible
5) Turn on the pump first and then immediately open the suction side valve