Air coming out of thin water?

[kmerkel]

The pool has a Doughboy Skim-Line Deluxe skimmer. When the pump is run with the skimmer in vacuum mode and vacuum hose attached, the water in the skimmer aerates, and the air seems to be entering through the vacuum port as I witnessed a stream of fine bubbles in the water. The vacuum hose was just purchased a couple weeks ago, so hopefully it's air/watertight. There are no outward water leaks from or around the skimmer, and the stream of bubbles is not there if the hose is not connected.

Aside from the possibility of a defective hose, I think I have it narrowed down to one of these theories:
Skimmer gasket leaks under heavy vacuum, but is fine with neutral pressure
Gases disassociating from the fluid due to heavy vacuum (this seems less likely)

Am I on the right track here? I'd like to get this figured out because I can't vacuum for more than a few minutes before the whole system aerates and messes up the filtration.

Thanks in advance!

 

[Texas Splash]

I don't think it's odd that you see some air in the system while vacuuming, but you should not lose prime to the pump to where you have to stop.

In comparison, I know when I vacuum, there is always more air in my pump strainer basket. Not sure if it's related to the strong suction pull and some form of outgassing that may occur. Never really thought about that. The hose is good and everything works well. Like you, as soon as I pull the hose out my pump basket is full again. I always figured it was just to mechanics of using a hose and slip-in fitting in the skimmer that is never as air-tight as the plumbing itself.

 

[kmerkel]

Thanks for reply.

To clarify, the pump doesn't lose prime (aka lose suction), but the water gets aerated enough that it percolates through the filter and bubbles come out of the return. If I don't backwash and rinse right after I turn the pump off after vacuuming, a cloud of dirty water comes out, too. So I guess I'm concerned that the aerated water is making the filter less efficient and negating the point of vacuuming in the first place.

 

[kmerkel]

Alright, time to revisit this. Since last year, I've downsized the pump and replaced the filter sand. The skimmer still gets aerated to the point that it affects function after about 10 minutes of vacuuming, and the cloud of nastiness still comes out of the return after I pause and restart the pump to burp the skimmer. What am I doing wrong?? Is this an equipment problem, or user error?

 

[Texas Splash]

It's still confusing when you say "the skimmer get aerated to the point it affects function". Are you using a skimmer plate with your set-up, or is the hose directly in the skimmer hole? Can you upload a pic of your equipment pad and maybe the pool side skimmer so we can see everything you have there?

 

[CrystalRiver]

Swivel fitting (if your hose has one) should be attached to the vacuum head, not the skimmer plate. They leak a bit, which is fine as long as it's under water.

 

[kmerkel]

It's still confusing when you say "the skimmer get aerated to the point it affects function". Are you using a skimmer plate with your set-up, or is the hose directly in the skimmer hole? Can you upload a pic of your equipment pad and maybe the pool side skimmer so we can see everything you have there?

Sorry, yes, I am using a skimmer plate and the hose is connected to the vacuum port of the skimmer. As for the aeration, I mean air will accumulate under the skimmer plate over the course of vacuuming, and after a certain point (water level drops below the vacuum port) the water aerates in the skimmer. I'm concerned that the aerated water is affecting pump and filter efficiency during vacuuming. Hopefully that makes sense?

I'll see if I can get a picture and/or maybe a video or two.

Swivel fitting (if your hose has one) should be attached to the vacuum head, not the skimmer plate. They leak a bit, which is fine as long as it's under water.

I'm just using a hose with an adapter for the skimmer plate, and the other end attached directly to the vacuum head.

 

[CrystalRiver]

I'm just using a hose with an adapter for the skimmer plate, and the other end attached directly to the vacuum head.

Yes, many hoses have one end that swivels. If you have that, the swivel end must be attached to the vacuum head.

 

[Texas Splash]

The aeration generated in the skimmer should not be a big problem for your equipment as long as the pump doesn't lose prime. I don't see where the filter plays any part in the scenario. But sometimes the skimmer plate just doesn't give an airtight seal which then can pull-in enough air to effect your vacuuming. Between the swivel adapter and the bottom of the skimmer, there's a good-sized void to fill and get air-tight. By any chance are you able to connect your vacuum hose directly into the skimmer without using the skimmer plate?

 

[kmerkel]

I'm not using a swivel, and the skimmer plate is completely submerged inside the skimmer. The only thing I can think of that could be a potential air leak is the outer skimmer gasket.

I will have to check again if the adapter will connect up with the skimmer outlet. My recollection is that it will not.

I mention the filter because of the plume of Crud that comes out only when I restart the pump during/after vacuuming. Could be correlation or causation.

 

[Texas Splash]

I mention the filter because of the plume of Crud that comes out only when I restart the pump during/after vacuuming.

Looking at some of your previous notes, the excessive air bubbles created between the skimmer bottom and plate could explain bubbles getting blown back out to the returns, much like a suction side air leak does the same sometimes. I can see why you would be concerned about the skimmer basket as well. With an AG set-up, maybe try some suction side air leak tests around that gasket?

But I can't see the correlation of crud getting blown-out of the return jets at startup. That just seems like a separate issue. When you opened up this year, did you do a sand deep clean or recall seeing anything odd with the sand? The Mystic sand should be okay, but I seem to recall a couple others users commenting about some odd behavior with that brand as well this year.

 

[kmerkel]

Hmm, testing for a suction side leak is a good idea if I can figure out how to do it. The vacuum port passage is pretty well buried below the weir opening. Maybe an exploded parts diagram will help visualize.



Going back to the filter, I was thinking that the combination of aeration and cycling the pump off/on is somehow breaking up the sand bed a bit, allowing dirt that would otherwise stay on or near the top to percolate through. That's just a theory I came up with in an attempt to understand what's happening and work towards a solution; it may or may not have any credence.

The sand is new this spring, done at the same time as the pump motor. It seemed OK to me when I poured it in and has worked well, save for this phenomenon when vacuuming.

 

[Texas Splash]

Hmm, testing for a suction side leak is a good idea if I can figure out how to do it.

Ha ha. Yeah, I see what you mean. Maybe something else you can try is with the pump off and water very still, check from the inside with some food dye to see if any seeps-out?

 

[Chasarms]

I have this same setup, and agree that’s it can be finicky.

The skimmer lid doubles as a slimmer plate. When you set it, make sure you don’t trap any air. I tip it as much as possible to prevent air under it.

Make sure the hose is thoroughly primed before you turn the pump on. I consider it primed when it sinks to the bottom.

Other than that, I have not had any issues. When I set it up right, it works. But if I somehow get air in it at the start, it will do odd stuff the whole time.

 

[kmerkel]

Well, there is no external water leak, so I don't think dye is going to work.
.

If the problem is the outer gasket, it's only leaking under vacuum. And at this point, I think I'm going to live with it for the season and wait until after closing to replace it.

The skimmer lid doubles as a slimmer plate. When you set it, make sure you don’t trap any air. I tip it as much as possible to prevent air under it.

Make sure the hose is thoroughly primed before you turn the pump on. I consider it primed when it sinks to the bottom.

I do both of those, every time. I bleed all the air out by putting one end in the vacuum port and the other in the return stream. My hose never sinks, though. Maybe mine is made of a different material? Everything stays under water when I hook up the vacuum head to the hose.

Other than that, I have not had any issues. When I set it up right, it works. But if I somehow get air in it at the start, it will do odd stuff the whole time.

At least you've given me hope that success is possible!