Skimmer Suction Air Leak - Hypothetical?

[JamesW]

It is a combination of the pump being off its BEP (best efficiency point) so its BEP would be between 70% and 120%

Australia uses 50 hz power, which is about 2,875 rpm for a single speed pump.

Pumps are usually designed for 60 hz/3,450 rpm so that they can be used with a 50 hz motor or a 60 hz motor.

So, that is probably where you are getting the 120% increase.

50 x 1.2 = 60.

 

[Texas Splash]

Mark,

1 - No air from filter air relief 10 seconds after first purge after running on high. We see te tiny bubbles flowing past the check valve and into the pump predominantly on high because that's when there is the most aggitation it seems. I think we see some on low as well, but the amount is much less so a bit harder to see them until they gather in the pot.

2 - Correct, the pot drops by about an inch or so and stays there, indefinitely so far. Water level doesn't change when pump is turned off. Only once in a while do we see a bubble pass through the check valve.

3 - Yes, 24/7. No times. I only turn it off to clean the filter or do maintenance.

 

[mas985]

Mark,

1 - No air from filter air relief 10 seconds after first purge after running on high. We see te tiny bubbles flowing past the check valve and into the pump predominantly on high because that's when there is the most aggitation it seems. I think we see some on low as well, but the amount is much less so a bit harder to see them until they gather in the pot.

Only 10 seconds but how about after 10 minutes? That may be too short to accumulate enough air. But seeing air bubbles in the check valve should confirm a leak before the check valve.

2 - Correct, the pot drops by about an inch or so and stays there, indefinitely so far. Water level doesn't change when pump is turned off. Only once in a while do we see a bubble pass through the check valve.

3 - Yes, 24/7. No times. I only turn it off to clean the filter or do maintenance.

I am starting to think that it is only high speed that may be leaking and it is far enough up the suction pipe that there is enough air in the suction pipe after a high speed run so that when switching to low speed, the leak stops but the existing air in the pipe moves to the pump basket and since the leak has stopped, no more air than what is already in the suction pipe can move into the pump basket so the level in the pump basket does not change after that.

A bit convoluted so hopefully makes sense and the only explanation that I can come up with that fits the evidence.

 

[Texas Splash]

Only 10 seconds but how about after 10 minutes?

I normally never run on high that lng, but I"ll do it when I get home as a test.

A bit convoluted so hopefully makes sense and the only explanation that I can come up with that fits the evidence.

Appreciate the in-depth analysis. Very frustrating on my end that I haven't found a definitive cause. I'm a human gopher and my backyard looks like prisoners have been trying to escape. Not extremely critical as the system is running and not losing prime. I'll keep you all posted if I should find something else that makes sense.

 

[mas985]

Australia uses 50 hz power, which is about 2,875 rpm for a single speed pump.

Pumps are usually designed for 60 hz/3,450 rpm so that they can be used with a 50 hz motor or a 60 hz motor.

So, that is probably where you are getting the 120% increase.

50 x 1.2 = 60.

Correct but when running a VS pump at 3450 RPM & 50 Hz it is still 100% of the design speed, not 120% of the design speed and the flow rate is still the same as it would be for 60 HZ. Nothing really changes as far as the pump and drive is concerned. The choice of 3450 RPM max speed is just by convention and the legacy of induction motors in the US. Remember the first stage of the VFD converts the AC to DC so it really doesn't matter what the line frequency is since it is rectified in the first stage.

 

[JamesW]

Correct but when running a VS pump at 3450 RPM & 50 Hz it is still 100% of the design speed, not 120% of the design speed and the flow rate is still the same as it would be for 60 HZ.

The person is probably used to single speed 50 hz motors and a speed of 2,875 rpm as the speed of a single speed motor.

So, when they see a 3,450 rpm motor, to them it is at 120% of the "normal" speed.

 

[JamesW]

As long as the pump is not losing prime, the problem is mostly being annoyed at the bubble.

 

[Texas Splash]

Only 10 seconds but how about after 10 minutes?

Mark, I just remembered to try this test. No change really. On high I still see the very tiny bubbles (really tiny) entering the pump, but since it's high speed they can't actually build up. After 10 min there was negligible air released from the filter air relief valve. It takes about 2-3 hrs for the air gap of about 1" to build back up under the lid.

 

[mas985]

Mark, I just remembered to try this test. No change really. On high I still see the very tiny bubbles (really tiny) entering the pump, but since it's high speed they can't actually build up. After 10 min there was negligible air released from the filter air relief valve.

You still see the air bubbles in the check valve after 10 min on high? It may take longer than 10 min for the filter to fill up if there aren't that many bubbles or the filter may be good at passing air out of the returns so it may not build up much.

It takes about 2-3 hrs for the air gap of about 1" to build back up under the lid.

This is on low speed though correct?

 

[Newdude]

the filter may be good at passing air out of the returns so it may not build up much.

His filter has an air relief tube at the top of the tank (on the inside) so there would never be more air than that.

This a different filter but same principle for anyone following and learning

 

[mas985]

Yes most do. Mine does as well but still can collect quite a bit of air at the top. Different designs probably have different amounts of air that can collect in the top.

 

[Texas Splash]

You still see the air bubbles in the check valve after 10 min on high?

No sorry, just the pump pot.

 

[Texas Splash]

This is on low speed though correct?

Correct.

 

[mas985]

1 - No air from filter air relief 10 seconds after first purge after running on high. We see te tiny bubbles flowing past the check valve and into the pump predominantly on high because that's when there is the most aggitation it seems. I think we see some on low as well, but the amount is much less so a bit harder to see them until they gather in the pot.

Maybe this didn't mean what I thought did?

 

[Texas Splash]

This has had me chasing my tail for quite a while now. I appreciate you going along for the ride. Today I started to fill-in my trenches, clean up work areas, and let the yard start mending while we have a few more nice days ahead. I'm starting to think this is just how things are going to be with new the pump set-up. I spent some time on the Anderson Manufacturing website yesterday, about the pull the trigger on a couple more leak detection toys, then decided to hold. I could order a skimmer saver (Frankenplug), but I'm not convinced there's a problem there either. When Look back at everything done so far:
- Passed/held water pressure testing in suction line for 30 min (12 -14 psi)
- No evidence of leak during static water dye testing in skimmer.
- New Power Flo Matrix pump (seals lubed of course), new check valve, and 2-way. Tried pressing (hard) on lid, no change.
- Inspected (visually and under pressure) the underside of the skimmer and plumbing in Aug when exposed.
- Visually inspected last remaining flex pipe on suction line just to be safe (all dry).
- No loss of prime, just an annoying 1 inch or so gap of air.

Perhaps I was spoiled with my Waterway Supreme's performance for about a decade with very minimal bubbles under the lid. This Power Flo Matrix seems to have slightly less power, so I can't help but wonder if that's part of it. Other than a a slightly different HP, both pump designs are practically identical.

I suspect I'll just let it ride for now and monitor. If/when the time ever comes down the road when I need a new pump, I'll definitely go with one of the more popular, robust VSPs and see if anything changes. If not, I may just cut a new trench (straight path) from skimmer directly to the pad. That would reduce my 90 degree elbows from 8 to perhaps 3 or 4 max. No rush on that though.

Time for a break. Have a nice weekend everyone.

 

[Texas Splash]

Since my last post in Nov, the water in that pump pot would continuously drop after about an hour of initial purge. In fact, the last week or so it would fall to the top of the white strainer basket inside. Not ideal.

Yesterday I vacuumed like normal, cleaned the filter, then purged the air like I've done hundreds of times expecting the pump pot to be able 3/4 full of water after an hour or so. This is what I found today. In fact, it was so clear I thought it was empty until I saw a few tiny bubbles floating around and my SWG all green with good flow. Besides vacuuming, the only other thing is we have had a substantial rain in the last few hours.

 

[mas985]

Higher water level with no air could be the answer. You will know for sure if/when the water level drops again.

Did you by chance also clean out the pump basket? Another possibility is that the lid has a better seal now.

 

[Turbo1Ton]

Since my last post in Nov, the water in that pump pot would continuously drop after about an hour of initial purge. In fact, the last week or so it would fall to the top of the white strainer basket inside. Not ideal.

Yesterday I vacuumed like normal, cleaned the filter, then purged the air like I've done hundreds of times expecting the pump pot to be able 3/4 full of water after an hour or so. This is what I found today. In fact, it was so clear I thought it was empty until I saw a few tiny bubbles floating around and my SWG all green with good flow. Besides vacuuming, the only other thing is we have had a substantial rain in the last few hours.

View attachment 545796

Unfortunately this sounds like a suction side leak, that is underground.

I had a similar issue with my pool. Water level would drop down over time, to the top of the pump strainer basket. I would have massive amounts of air to purge out of the filter every day. When we would get a good soaking rain, it would go away, just as yours has done. I tried lots of things, I built a smoke machine to inject smoke into the suction lines through the pump drain plug, to see where it was leaking. Finally I got frustrated, took the hose out there, which I had done several times already, and ran it over the pump lid/drain plugs/inlet union, the leaf canister lid, everything I could see, and finally when I let it saturate the ground around the base of the leaf canister, the air started going away. Mine turned out to be a loose union at the bottom of my A&A leaf basket. I rebuilt the entire section between it and the pump just in case it was more than the union.

Hoping that it is not an underground leak, for your sake. Maybe it is just the pump lid seal, like mas95 alludes to, or something above ground that is easy enough to get to.

--Jeff

 

[Texas Splash]

Did you by chance also clean out the pump basket? Another possibility is that the lid has a better seal now.

I did yesterday after vacuuming. My concern about the lid is I took out on and off several times last month when trying to diagnosis the issue. Certainly is odd though.

 

[Texas Splash]

Hoping that it is not an underground leak, for your sake.

Yeah, this was a thought as well, but I pressure tested the line a few times and it held. I had virtually all of it exposed as well. I do have a concern about the first couple inches into the skimmer before the PVC which is why I was contemplating a Frankenplug in the skimmer hole. But being under the concrete decking, I would think the rains would not have effected that area to cause a change.