Skimmer Suction Air Leak - Hypothetical?

[Texas Splash]

Excluding everything above ground at the equipment pad, when it comes to a suction side air leak, we often think of a cracked fitting, PVC pipe, etc. This is typically anywhere between the pump inlet going backwards (to the pool) underneath and up into the bottom of the skimmer where the suction line connects. Just like a big straw.

So here's my question - If that suction line from the pump inlet to the bottom of the skimmer is 100% air tight (pressure tested), can air still get pulled into a suction line from the inside/bottom well area of a skimmer where the basket sits? Since that area is generally submerged, I'm wondering. I'm thinking yes, but I rarely see it discussed. Thoughts?

 

[Jimrahbe]

Pat,

On the surface, I don't see how...

Why do you ask???

Thanks,

Jim R.

 

[Newdude]

My PB explained the VS pump bubble as cavitation from all the burrs and uneven edges at the fittings between the skimmer and pad.

Just this weekend I noticed a 1/2 inch burr inside the skimmer pipe while blowing it out. It's a 90 directly from the skimmer and I had one in the few inches I could see. I believe we always had 'the bubble' but it wasn't noticeable with single speed pumps.

So I'll raise you this thought, that the pipe is 100% leak free, and the air is being created internally along the way.

I also don't see how the skimmer and pump pasket don't create some level of aeration, no matter how small.

 

[Texas Splash]

Why do you ask?

I'm experiencing some unusual air and in the past few months I have literally replaced just about everything (most of the line, pump, valves, etc) but the skimmer which I know has shifted (tilted) and has some stress cracks. My dye tests in static water we not conclusive. I've done some epoxy & silicone touch-up work inside the skimmer, but I am thinking I may have missed a spot. There wasn't anything that ever leaked water that I could tell. Nothing I could find when I had the skimmer exposed during my suction line repair in August, but I'm suspicious of that lower area in the skimmer. Since a pressure test only covers the line itself (skimmer hole to the pad), it got me to thinking about the lower half well area of the skimmer.

 

[Texas Splash]

o I'll raise you this thought, that the pipe is 100% leak free, and the air is being created internally along the way.

Interesting concept. Mine is a bit more than just a few bubbles though, but I suppose it makes sense.

 

[Newdude]

I've done some epoxy & silicone touch-up work inside the skimmer, but I am thinking I may have missed a spot.

90 up a test pipe from the skimmer threads, through the weir door and a foot into the pool. (For test purposes only, while respecting the suction dangers)

 

[Texas Splash]

90 up a test pipe from the skimmer threads, through the weir door and a foot into the pool. (For test purposes only, while respecting the suction dangers)

Oooooh, that is an interesting test method. I think I'll give that one a try.

 

[JamesW]

There was a skimmer that had a black bottom that was known to leak pretty bad and they created an epoxy repair kit for it.

Black Bottom Products Epoxy Skimmer Repair Kit | BBP-1 Parts

If the skimmer was not airtight, it might pull in air, but the suction would need to be pretty high.

It is unlikely that the air is getting in at the skimmer.

It is not being produced on the way.

Skimmer Epoxy Kit

I'm going to guess my skimmer is leaking. [attachment=0:13qb1tlh]IMG_1416.JPG[/attachment:13qb1tlh] Water level has been stuck at the lip of the skimmer for a couple of days, and the water has remained at the same level in the pipes. I have the dreaded "black bottom skimmer". You can see an...

www.troublefreepool.com

 

[HermanTX]

One way is if there is a vortex created such that it can suck air from the surface tension of the water.

 

[JoyfulNoise]

Remember that the suction force (vacuum) is at a maximum inside the pump and that relative vacuum “pressure” decreases as you get further away. Inside the skimmer body itself, there is very little suction force below the nominal air pressure.

I would check your pump lid seals and especially the wet end plugs.

@JamesW will supply us with a simulation of pressure and flow of the full Navier-Stokes equations using finite element analysis simulations of your entire plumbing system.

I would like him to simulate both Newtonian fluids (water) and non-Newtonian fluids (eg, Ketchup) in his analysis.

 

[JamesW]

@JamesW will supply us with a simulation of pressure and flow of the full Navier-Stokes equations using finite element analysis simulations of your entire plumbing system.

I would like him to simulate both Newtonian fluids (water) and non-Newtonian fluids (eg, Ketchup) in his analysis.

Sorry, that requires a “Premium” subscription.

With your basic access, you only get the simplified Lagrangian models, which are based on the principle of least action.

The geometry is basic Euclidean geometry and only the basic axiomatic theorems are employed.

 

[JamesW]

and non-Newtonian fluids (eg, Ketchup) in his analysis.

Why is your skimmer full of ketchup?

Have you been listening to the Facebook group again?

Do you put the ketchup on the sponge or do you remove the sponge and the copper pipe before using the ketchup?

The ketchup will help dissolve the copper pipe, but seriously, stay away from the Facebook group.

 

[JoyfulNoise]

I was using toothpaste to remove some calcium scale but the fluoride reacted with the calcium and made the scale really hard … I guess my pool doesn’t have to worry about tooth decay now However, being a thixotropic fluid with non-linear sheer strain properties, I think all the toothpaste made the pump cavitate … I dunno, maybe I should use Colgate instead of Crest pool care is such a pain sometimes …

 

[Texas Splash]

Question for those who know hydraulics well (i.e. @JamesW, @mas985 , etc) or other like experiences. Is it possible that a pump could be underrated or under-performing for a pool to the point it may display symptoms that mimic that of a suction air leak? By that I mean the pump is slow to prime and the pump pot does not remain completely full after prime. The pump pot water level drops a few inches after about an hour, then remains there, with a lot of churning which looks like air trapped and struggling to leave the system.

I always assume air leak, but could poor pump performance do the same?

 

[JamesW]

Maybe a video of the pump running and turning on and off would be helpful.

 

[Texas Splash]

Not sure this link will work. If not, I'll try another one when I get home.

New video by V F

photos.app.goo.gl

 

[JamesW]

Is that on low speed?

That's common on slower speeds.

I do not know why it happens.

As long as it does not lose prime, it should be ok.

 

[JamesW]

Maybe pressure test the entire system at once to include the pump, filter, suction and returns.

 

[Texas Splash]

Yes, it is low speed. For 10 years I had my Waterway Supreme. Always on low. It maintained a 98% full pot up until this season where it started to drop a little. I did some suction line inspection/repairs (pressure tested) as of late and it helped, but then I decided to install the new Power Flo Matrix I had laying around. New pump, valves, etc. I can post motor labels later, but the Matrix seems to be a slightly lower rated pump than the Waterway. Got me to wondering if it's able to sustain the pull of about 40' through approximately 10 elbows.

FYI - I took that 10 yr old Waterway last night and rigged it up next to the pool on the decking with a short in & out PVC line directly to/from the pool. Pump pot is 100% airtight and water full with not a spec of air in it. But to be fair, it's right next to the pool and no filter resistance.

 

[Texas Splash]

Maybe pressure test the entire system at once to include the pump, filter, suction and returns.

That may indeed be my next step.