Air leak gets worse at lower pump speed

[nostaljake]

I've been dealing with a small air leak in my system that I've been trying to figure out. This is on the deep skimmer line.

I know it's the deep skimmer because I have check valves on all three lines (shallow skimmer, deep skimmer, main drain). The shallow skimmer and main drain check valves never have air bubbles. The deep skimmer one always does.

I already replaced the cover of the check valve with no luck. The line is mostly above ground, so I also carefully inspected it going all the way back to the pool (until it goes underground near the skimmer) with no luck.

Today I noticed the air bubbles in the valve are reduced significantly when I turn the pump speed higher. I run the pump 24/7 because the equipment pad is far away from the pool and slightly elevated. I usually run it at 2,200 RPMs. Today I was running it at 2,800 and there was a noticeable decline in the number and size of bubbles in the check valve.

What can cause this? Does this give us any clues to the source of the leak?

 

[PoolStored]

VSPs are notorious for "gaining air" at low speeds. Lots of threads here. The supposition is that at low speeds, there is less vacuum, allowing small amounts of air into the pump basket.

I'm not sure what a "deep skimmer" is...but if it is farther away, then it is not drawing as much pressure as a close skimmer. This would make the problem worse.

I've pressure tested my system. It will hold 15psi for 12 hours. I get a bubble in my pump.

Here is what I found to work the best.

Get a new o-ring for the pump basket cover.
Fine sand the volute with a flat, hard sanding block with 3000 grit sand paper.
Clean the cover lid.
Lube the new o-ring with silicone lubricant like Magic Lube II (do not use PTFE/Teflon lubricant). DO NOT use silicone SEALANT.
Re-assemble.

Run your low speeds as normal, setup one of the 4 speeds to run at 3000rpm for 15 minutes during the 24 hour period. This will clear any bubble.

A list of threads I've responded to with the same problem...

Search results for query: bubble

www.troublefreepool.com

 

[nostaljake]

VSPs are notorious for "gaining air" at low speeds. Lots of threads here. The supposition is that at low speeds, there is less vacuum, allowing small amounts of air into the pump basket.

I'm not talking about air in the pump basket, though. There is air in the check valve on the deep end skimmer line. So before it gets to the pump basket. There is NO air in the check valve for the shallow end skimmer or the check valve for the main drain.

If I close the deep end skimmer line and run only the other two, there are no bubbles. So it's definitely an issue with the deep end skimmer line specifically.

 

[HermanTX]

If I close the deep end skimmer line and run only the other two, there are no bubbles. So it's definitely an issue with the deep end skimmer line specifically

I think you stated that you examined a majority of the deep end skimmer line and could not find a leak.
Is the check valve the only fitting on the line from the skimmer to the equipment pad?
Put plastic wrap around the check valve to determine if that stops air into the check valve. If it does then the leak is on the body of the check valve.
Do the same for any fittings on the exposed plumbing.
Also check that the weir door is not stuck which could allow air into the skimmer as the water is sucked down.

 

[nostaljake]

Is the check valve the only fitting on the line from the skimmer to the equipment pad?
Put plastic wrap around the check valve to determine if that stops air into the check valve. If it does then the leak is on the body of the check valve.
Do the same for any fittings on the exposed plumbing.
Also check that the weir door is not stuck which could allow air into the skimmer as the water is sucked down.

Well, the line is VERY long, so there are a few couplings. Most of the line is like half buried, so I previously dug a shallow ditch and filled it with water by all the connections to see if it changed anything (it didn't). I tried the plastic wrap today and didn't notice a difference, but it was difficult to get a good seal with the wrap, so I don't think we can make too much of that.

I'm definitely suspicious of the skimmer itself. It looks old and whoever owned the pool before me used a bunch of putty right at the entrance. I guess to patch a leak? Not sure that should matter for the air leak, but the whole thing seems shoddy. Anyway, the weir seems like it's working correctly to me, but I could absolutely be wrong about that.

Also, I realized I was wrong about something I posted earlier. I tried closing the deep end skimmer line again, and although there were no bubbles in the check valves, there WERE still bubbles coming out of the return. There were actually MORE bubbles, I'd say. So now I'm really confused.

I also tried the opposite -- closing the shallow end skimmer and leaving the deep skimmer and main drain open. Same thing. More bubbles in the return than previously. So there are fewest bubbles when all three lines are open.

Maybe I have multiple air leaks? The part that confuses me most is the check valves. I never have air bubbles in the shallow end check valve or the main drain check valve. Always in the deep end check valve. The deep end check valve is the only one that's horizontal... the other two are vertical. Does that matter at all?

 

[nostaljake]

Posting a photo of my equipment pad suction side in case it helps:

 

[PoolStored]

Clean/backwash your filter and see what happens…

 

[nostaljake]

Clean/backwash your filter and see what happens…

Filter is new and this same problem has existed since before the filter was replaced

And isn't the filter pressure side anyway?

 

[nostaljake]

Tried running each line separately. Bubbles in the return in all three cases. But more problems with the deep skimmer:

main drain only = bubbles in return, water shoots out filter as soon as air release valve opened
shallow skimmer only = same as above
deep skimmer only = bubbles in return, pipes shaking, lots of air in filter

So I still think there's a problem in the deep end skimmer line. Although it seems like there's another problem too?

 

[nostaljake]

Running all three lines together again, and virtually no bubbles in the returns now. Still a couple tiny bubbles in the deep end skimmer check valve.

 

[HermanTX]

Also, I realized I was wrong about something I posted earlier. I tried closing the deep end skimmer line again, and although there were no bubbles in the check valves, there WERE still bubbles coming out of the return. There were actually MORE bubbles, I'd say. So now I'm really confused.

Could indicate a pressure side air leak (from the filter to the pool return) But that could also show a water leak which you have not mentioned.
The filter will capture air which is why there is a relief valve to manually bleed air out of it.

The part that confuses me most is the check valves. I never have air bubbles in the shallow end check valve or the main drain check valve. Always in the deep end check valve. The deep end check valve is the only one that's horizontal... the other two are vertical. Does that matter at all?

If there are bubbles they will show in a check valve that is horizontal more than in one that is vertical.
Also, you point out a main drain check valve that this not accurate (unless it is not shown in the photo) - that is a 3-way valve and it is shown to be open to both the main drain and any flow from whichever skimmer is open. You can rotate the valve to completely shut off the skimmers and only have suction from the main drain.

Question - Is your equipment pad higher than the pool water level?
Question - when you are doing the testing on each line - is the VS pump at the same speed? Higher RPM’s will dissipate bubbles faster.

Question - it is shown that spa main drain is collapsed - so this is a non-functional line from the spa. Correct.

 

[nostaljake]

Could indicate a pressure side air leak (from the filter to the pool return) But that could also show a water leak which you have not mentioned.
The filter will capture air which is why there is a relief valve to manually bleed air out of it.

If there are bubbles they will show in a check valve that is horizontal more than in one that is vertical.
Also, you point out a main drain check valve that this not accurate (unless it is not shown in the photo) - that is a 3-way valve and it is shown to be open to both the main drain and any flow from whichever skimmer is open. You can rotate the valve to completely shut off the skimmers and only have suction from the main drain.

Question - Is your equipment pad higher than the pool water level?
Question - when you are doing the testing on each line - is the VS pump at the same speed? Higher RPM’s will dissipate bubbles faster.

Question - it is shown that spa main drain is collapsed - so this is a non-functional line from the spa. Correct.

Thanks for your help!

I thought bubbles in the return means it has to be a suction side leak? To clarify, there are ALWAYS some bubbles in the return. If all three lines are open, there are far fewer. But they're still there.

Not ruling out that I have a pressure side leak too, but I thought that only resulted in a water leak? I'll do a bucket test soon, but I'm not noticing any crazy water loss.

And yeah, that was bad labeling in the photo, my bad. The check valve is kind of behind the 3-way valve there, lower to the ground.

Question #1 -- YES. It's maybe 6 feet higher. And a long run from the pool, maybe 50-60 ft.
Question #2 -- Yes, I tested all three lines both at 2,200 and 2,800 RPMs. More bubbles at 2,200 but lots of bubbles at both speeds (when only one line running). Far fewer with all three lines open.
Question #3 -- Correct. The spa drain is presumed to be collapsed, according to the pool company the previous owners used. It is definitely non-functional.

 

[arvil]

Sounds like it could be the pump seal since you always have bubbles. This is the seal where the motor shaft goes into the pump housing. The shaft will be at the vacuum part of the pump, if the seal is worn, it could allow air intake.

 

[PoolStored]

Sounds like it could be the pump seal since you always have bubbles. This is the seal where the motor shaft goes into the pump housing. The shaft will be at the vacuum part of the pump, if the seal is worn, it could allow air intake.

A shaft seal will leak water, it is on the pressure side of the pump.

 

[HermanTX]

Question #1 -- YES. It's maybe 6 feet higher. And a long run from the pool, maybe 50-60 ft.

OK that makes sense as to why each line has a check valve.
Let’s focus on the suction side as that is main component that would pull air into the system.
Have you checked the drain plugs on the pump? You can back each out, lube and reinstall. The other is the pump lid as discussed earlier.
If there is air in check valve then the suction leak would be before that on the plumbing line at a fitting most likely or the check valve itself.

Have you take a hose and run water over each fitting/check valve/3 way valve to confirm each is ok. Running water will momentarily shut off air and help pinpoint a possible air leak. This will help fine a crack in a body of a valve or a fitting.
Alternatively you can wrap handi-wrap tightly around each to close off a crack.

 

[nostaljake]

OK that makes sense as to why each line has a check valve.
Let’s focus on the suction side as that is main component that would pull air into the system.
Have you checked the drain plugs on the pump? You can back each out, lube and reinstall. The other is the pump lid as discussed earlier.
If there is air in check valve then the suction leak would be before that on the plumbing line at a fitting most likely or the check valve itself.

Have you take a hose and run water over each fitting/check valve/3 way valve to confirm each is ok. Running water will momentarily shut off air and help pinpoint a possible air leak. This will help fine a crack in a body of a valve or a fitting.
Alternatively you can wrap handi-wrap tightly around each to close off a crack.

I'm skeptical of the pump being the issue because (a) the pump is new this year and (b) the bubbles in the check valve are obviously before the pump. But I'll double check.

I did previously run water on each fitting on the deep end skimmer line (the one with bubbles in the check valve). No change. I can't get at the fittings close to the pool where it connects to the skimmer, but otherwise I checked all the other connections which are above ground.

I'll try running water over all the valves/fittings at the equipment pad, but it's hard to see into the pump basket on the Calimar, so not sure I'd even be able to notice a change. And while that might help find a leak, it can't be the leak that's showing in the check valve, right? That one has to be somewhere before the check valve or in the valve itself, as you mention.

 

[arvil]

@PoolStored: Oops! Forgot abought behind the impeller back the space would be connected to the outside of the impeller, the pressure side. My bad.
I wonder if maybe the pump drain plug o ring may be leaking under vacuum.

 

[nostaljake]

So had some strange luck with the air leak, and again I'm confused about it. We had a power outage here yesterday, so the pump was off for several hours (it normally runs 24/7).

When I turned the pump back on, I opened the main drain first. Got prime immediately. Then the shallow end skimmer. Got prime immediately. Then the deep end skimmer that has the bubbles in the check valve. That took like 5 minutes to get prime.

And now there are no bubbles coming out of the returns. Literally zero as far as I can tell. There are still bubbles in the check valve of the deep end skimmer, so not sure if I'll eventually start getting bubbles in the returns too. But it's been like 36 hours and there are zero bubbles in the returns.

I'm running the pump at its normal operating speed of 2,200 RPMs. Obviously I did use full speed to get prime, but I lowered it back to 2,200 right after.

I have no idea what to make of this. @HermanTX and others, let me know what you think!

 

[HermanTX]

Well strange things happen with a pool. The fact that you see bubbles in the check valve tells me that there is still a air leak on the suction line somewhere. It is small so just monitor it over the next several days.
Ensure you bleed your filter of air so it is full of water.

 

[nostaljake]

Update: I've been running the pump at 2200 rpms for the past two weeks, all with zero bubbles in the returns. Bleeding the air in the filter periodically (but very little in there).

Today I put the pump at full power for like 10 minutes to help clear debris at the surface. When I decreased the speed back to 2200, there were lots of bubbles in the returns again.

After that, I fiddled around with it at varying speeds, seeing varying amounts of bubbles. Currently I've got it running at 2800 with some bubbles.

So... I still don't know what to make of this. Why was I able to run the pump at 2200 for two full weeks with no bubbles? Is it possible there's some luck involved with the vacuum? Like, when the speed gets shifted, it sort of "locks" the amount of air that comes in (or not), and I got lucky that one time and it locked the air out?