Can someone explain this to me - air bubbles in pump lid solved

[Krulligo]

So last year I ran my pool with completely no air bubbles in the pump lid. At the start of this year, I had my pool liner and skimmer replaced and once finished, I have since then always had a smaller pocket of air in the basket lid. I thought this was a problem of the plumbing that joins the skimmer (since this was reattached to the new skimmer). However, after retightening all the suction side plumbing before the pump, and looking for air leaks in both the plumbing (with soap suds and smoke), as well as any inspecting/cleaning/adding silicone lubricant to any gaskets/o-rings including the large o-ring in the pump lid I could not detect an air leak. Whenever, I stopped the pump, I would look whether water was coming out of any of the joints in the plumbing and it never did. Becoming frustrated, I decided to just leave it alone as it was quite a small air bubble and did not affect the flow of water. It was also not a water level issue.

We recently got quite a bit of rain and I needed to do a backwash anyway, so I backwashed and rinsed some water out of the pool to drop the water line to where it should be. Low and behold, after backwashing/rinsing, the air bubble in the pump lid has completely gone away and now no air is being drawn into the pump. The lid is completely filled with water.

How did the backwash fix this issue. I thought that that air in the pump lid is a result of air being sucked in somewhere on the suction side (plumbing before or at the pump). However, the backwash (and switching the sand filter to backwash-->rinse-->filter position) has solved this issue. I thought anything with the sand filter is considered pressure side. Can anyone explain this? I am glad it solve my issue, just puzzled.

 

[Jimrahbe]

K,

Some air under the pump lid when running at a low RPM is quite normal.

On my system, I have noticed as my filter gets dirty, the air under the lid will increase. Still not a lot, but definitely an increase.

We have also seen a number of posts like yours noting that a backwash, or filter cleaning, seems to reduce or eliminate the air under the filter lid.

My "guess" is that nothing is perfect and that most systems have very tiny suction side air leaks. Over time these small leaks cause the bubbles we see under the pump lid. A dirty filter just makes these little leaks worse as there is less of a suction vacuum as the filter gets dirty.

No matter what the actual cause, the issue of small bubbles under the pump lid at low RPMs, seems to be almost universal. And, unless they keep getting bigger and bigger over time, they do not seem to cause any issues with the normal system operation.

Thanks,

Jim R.

 

[Krulligo]

Hmm. It's still weird to me cause last year and the year before that, I never had any issues like this. The pump lid was completely full of water, and when I say completely full, there are absolutely no air bubbles (it actually makes it look like there is no water in the pump lid cause it's 100% full of water with no air). So I never had what you described as "normal" in always having a small amount of air until this spring when my liner/skimmer was replaced. However the recent backwash has solved the air and now it's back to how it was past couple of years - completely filled with water and absolutely no air)

If it was due to dirty filter/sand I should have also seen this happen past couple years.

 

[Jimrahbe]

K,

I did not mean to say that without a doubt every VS pump will have air bubbles under the lid, just that it is very common.

I would consider yourself lucky..

There are a number of places where a very tiny leak could occur, so having them all seal perfectly is kind of lucky. Keep in mind that I am talking about very small air leaks that would be almost impossible to find or even notice if the bubbles did not collect under the pump lid.

I went down this rabbit hole a couple of years ago. I bought a new lid for my pump, replaced the O-Ring under the pump lid, rebuilt all my suction-side Jandy valves. etc, etc. I got nowhere. The bubbles would often go away but would be back within a day or so. This is when I first noticed that cleaning my filter would decrease the amount and size of the bubbles under the pump lid.

So now, my advice is to just ignore the bubbles unless they start to cause some issue with the way the system is working.

Thanks,

Jim R.

 

[arvil]

If the bubble is stable and not significantly increasing, no problem as long as the water flow is good. I usually have a bubble in mine. It’s when you start blowing bubbles out the return then there’s a problem on the low pressure side.

 

[Krulligo]

If the bubble is stable and not significantly increasing, no problem as long as the water flow is good. I usually have a bubble in mine. It’s when you start blowing bubbles out the return then there’s a problem on the low pressure side.

Yes I understand this and that is why after trying to solve the issue, I just decided to live with it. Was just quite surprised that it was solved with a simple backwash, and was confused as to the reason why a backwashed solved this. Just wanted to hear peoples thoughts on an explanation.

 

[Bperry]

Yes I understand this and that is why after trying to solve the issue, I just decided to live with it. Was just quite surprised that it was solved with a simple backwash, and was confused as to the reason why a backwashed solved this. Just wanted to hear peoples thoughts on an explanation.

If an air bubbles does form at the top of the lid, the pump has no way to force the bubble down to the bottom of the chamber and out of the system. (Air bubbles rises upward) If I increase the pump speed, sometimes that’ll dislodge the bubble enough to break it into smaller bubbles and get mixed in with the surrounding water and get passed through to the returns. I’d imagine that backwashing may do the same thing.

 

[Jimrahbe]

K,

I just now noticed that you have an AGP. This means that gravity is pushing water into your pump, so I am not surprised that you normally don't have any air bubbles.

In ground pools use 'suction" to suck the water out of the pool. This suction can also suck in air at any of the connections or valves along the way.

Thanks,

Jim R.