Is air in pump basket while running normal?

[kabbak]

See my sig for setup.
The basket isn't completely filled. I can see the horizontal "column" of water entering the basket from the inlet pipe (supply is 1.5", exit is 2"). I'm not talking bubbles like from cavitation, it's just not filled and is stable like this while running.
Skimmer looks well filled, if anything pool level is too high (recent rains). It seems unlikely air's entering from there and the air condition is not intermittent.
I checked that the basket cover is well seated on clean o-ring.
I estimate pump is 22' from pool. Pool has single bottom drain and single skimmer on end of pool nearest pump.
Pump seems pretty noisy too.

Is the pump too big for the inlet plumbing? I've been considering reducing to 3/4 HP SF 1.27 or even SF 1.
Any thoughts on what's going on or what to check.
Thanks so much for your help!

 

[Bama Rambler]

The only time I've seen my pump do that is when the skimmer basket was full and restricting the flow. It could also be caused by partially obstructed suction piping. That's not good for your pump.

 

[denisbaldwin]

Mine does that too. The pump never fills completely up in the basket. It doesn't matter whether I turn on or off the skimmer, main drain or cleaner inlet. It does it with any of the 3 on or all of them on. The water flows, fills up to the inlet pipe and sometimes to the top of the pump basket, but never completely solid with water.

This has been true of both the 2HP Hayward and now my 3/4HP Hayward. I've replaced inlet pipes as far as I could (to the concrete underground), valves and had the rest of the pipes snaked and it's still doing it. Not sure what to do, but the pump seems to be running fine (and quiet), so I hadn't put much though into it.

 

[JohnT]

No, it's not normal. It indicates that either you don't have sufficient water flow into the pump due to a restriction at the skimmer or drain, or in the pipe, or that you have an air leak in the plumbing between the pool and the pump impeller.

The drain plug on the bottom of the pump strainer basket, the strainer basket lid, unions, valves or any fitting on the line are the most likely leak locations.

Any unexplained little drips of water when you shut the pump off?

 

[mas985]

Also, how high is the pump above the pool's water line? And what is the filter pressure?

 

[kabbak]

In my case, and according to a guy who has "plumbed 5000 pools" who visited today (for other reasons not pool related) my supply lines from skimmer and drain are 1.5". Out of pump they are 2", but pool returns are two lines with ~1" eyeballs and the pool cleaner line.

He says my pump sound is called "rattling". He also suspects leaks in supply side.

His primary observation is that impeller may be damaged/clogged with Crud and not pulling enough head.

I've no leaks around pump/filter except from outlet pipe fitting of PB4 booster pump (to be retaped very soon).
System 3 filter pressure is 10psi.
Pump is about 1 - 2' above pool water level. (I need a long clear hose )
FWIW, I don't have any valves between pool skimmer or drain and the returns to pool.

I'm surprised that denisbaldwin's system didn't resolve after changing to a, presumably, much lower head pump if starvation is the issue. However, I'm quite puzzled.

Any point in adding a pressure/vacuum gage on INLET to pump to help diagnose this?
Thanks!

 

[JohnT]

It sounds like the guy you talked to knows his stuff. Here's what I would do. Pull the pump basket out and reach into the hole going to the impeller (with the pump off ) See if you feel anything in there besides the impeller. If you do, you probably want to disassemble to pump and clean it up. If there isn't a bunch of stuff in the impeller, place a garden hose into the inlet side of the pump basket, and wrap a rag or towel around it to seal it off. Water should flow easily back to the pool.

 

[Pool-creetin]

Glad I read this, I thought it was normal to have a little air in the pump basket. The last pump I had lasted 12 years so I didn't think of it much. Always learn something new. Glad I found this site! Good luck kabbak!!!

 

[kabbak]

Latest update on my findings:
Using my fingers to probe, pump impeller doesn't feel like there's anything in the center or at entry to vanes. Of course, it's very hard to tell without removing pump housing.

I tried JohnT's recommendation to pump water with a hose backwards through pump intake. Hose flow isn't very high compared to pump, but it worked fine, the flow appeared at the skimmer basket and no junk emerged.

I also tried temporarily removing the "diverter" at the bottom of the pump basket to minimize restriction on the intake line. This had no discernible effect on the flow in the pump.

I suppose I could rig a pressure test of the line to see if it leaks.

I did discover that the System 3 filter is draining when pump shuts off because of a leak at the inlet seal ring to the filter. If I slightly tilt the whole system 3 toward the inlet the hissing and draining stops. It's very hard to turn the seal ring in either direction.
Is there a tool for dealing with these rings? A giant filter wrench perhaps?

To clarify an earlier comment I made, the plumbing to and from the pool is 1.5". It was built in '74.

FWIW, filter PSI is reading 8.5 to 9 when running and after air purge of filter.

So, I'm still puzzled about the air in the basket. :?

Thanks for reading.

 

[mas985]

Try pouring water over the pump basket and valves via a hose and see if the air disappears. Also, has this always occured?

 

[kabbak]

Try pouring water over the pump basket and valves via a hose and see if the air disappears. Also, has this always occured?

FYI, there aren't any valves between pool and the returns.

I also applied thin film of silicone grease to the o-ring under basket lid after carefully cleaning both to minimize likelihood of leak.
However, I understand your suggestion and will try it.

I'm currently wondering whether this pump/motor combo draw more (I figured ~80 gpm with 9psi at filter) than my 1.5" piping can supply and the resulting pressure differential in the basket is near enough to vacuum to be continuously degassing the water into the basket. Hence the continuous air supply.

Thanks Mark!

 

[duraleigh]

I doubt that the air is from restriction of the intake. You could confirm that by partially blocking the intake further either through a valve you may have or restricting it at the skimmer.

Have you checked the drain plug at the bottom of the pump basket. Many pumps have two. Maybe even wrap a couple of turns of teflon around them to make sure you have a good seal at that point.

 

[mas985]

Do you have a single 1.5" suction line and again, has it always been this way or did it just start doing this?

 

[kabbak]

Do you have a single 1.5" suction line and again, has it always been this way or did it just start doing this?

Well, I'm not positive re the 1.5" suction. What I see is a single 1.5" pvc pipe from pad's concrete to pump. Another two 1" PVC lines to/from PB4 booster pump also emanating from the pad. And then a 1.5" copper pipe into the pad from heater that returns to pool.

Sorry, I neglected to answer this. I don't know history of this problem as recently bought property from bank so nobody knows nuthin, but it's been the case for the month I've had an eye on it.
Thanks!
-Keith

 

[mas985]

If you have a single suction line, then the pump could be starved for water which would explain the lowish PSI. One way to tell is to restrict the return side flow some as see if the pump basket fills up.

 

[kabbak]

If you have a single suction line, then the pump could be starved for water which would explain the lowish PSI. One way to tell is to restrict the return side flow some as see if the pump basket fills up.

An interesting discovery.

With two helpers one covering each of the two eyeball returns, the pump basket fills and becomes quiet. From this I leap to the conclusions that either, there's an obstruction somewhere in the intake piping, or the pump is oversized for the return head/intake plumbing.

Have people actually encountered a blockage in intake piping itself? The opening at the skimmer is clean and clear.
Is there a plumbing snake I can use on 1.5" PVC?

Regarding the pump, can I just change the motor to a 3/4HP SF 1 unit from the current 1HP SF1.5? Can this be done without removing the pump since it's hard plumbed in place. i.e., no disconnects, unions etc. except to the system 3 filter.
Am I nuts ?
Thanks!

 

[denisbaldwin]

Have people actually encountered a blockage in intake piping itself? The opening at the skimmer is clean and clear.
Is there a plumbing snake I can use on 1.5" PVC?

I just used a drain king to dislodge a huge leaf and fur mess that had all but completely clogged my skimmer. Water was still flowing, but no where near the rate it should have. I still have air in my pump basket, but it's just at the lid level now instead of half way up the basket wall like it was before.

Denis

 

[mas985]

It could be a blockage although it could be that the suction pipes are too small since you really don't know if it ever worked properly. The first thing to do is to rule out a blockage but I think you said that you had already done that. Back flushing through the pump inlet should tell you if there is a problem or not.

Also, a pump's power is determined by the impeller not the motor. The motor just needs to big enough to support the impeller. To reduce the size of a pump, you need to reduce the size of the impeller. In fact, you can keep the old motor and just replace the impeller if you want to. That will reduce the flow rate, head loss and energy costs but it may not completely solve the plumbing issue although it should probably help.

If it isn't blockage, then the easiest solution would be to use smaller return eyeballs. This would increase the return head loss such that the suction would decrease.

 

[kabbak]

Have people actually encountered a blockage in intake piping itself? The opening at the skimmer is clean and clear.
Is there a plumbing snake I can use on 1.5" PVC?

I just used a drain king to dislodge a huge leaf and fur mess that had all but completely clogged my skimmer. Water was still flowing, but no where near the rate it should have. I still have air in my pump basket, but it's just at the lid level now instead of half way up the basket wall like it was before.

Denis

Genius minds. I just ordered a couple of drain kings in various sizes for pool use and rainwater drains.
I tried sending a 1/4" snake into the skimmer and pump ends of the suction line, but wasn't able to get it in more than maybe 8" due to 90 degree bends. Interestingly, upon starting pump back up, it was filling much more completely and filter pressure had risen from < 9 to 12.5. Hadn't ever seen that upon startup.
However, two days later it's back to not filling and the < 9psi pressure.
I'm looking forward to that drain king!
Thanks for your update. Very useful!

 

[kabbak]

It could be a blockage although it could be that the suction pipes are too small since you really don't know if it ever worked properly. The first thing to do is to rule out a blockage but I think you said that you had already done that. Back flushing through the pump inlet should tell you if there is a problem or not.

Not sure my hose in the pump really qualified as a reliable back flush as seal may have compromised peak pressure. Hence the drain king I ordered and look forward to trying.

Denisbaldwin's results and my brief one with a snake are encouraging.

To test line clearance, I was thinking of threading a jawbreaker on the end of some heavy monofilament line and slowly feeding it into the skimmer end of the suction line until it appears in pump's basket. I figured if I could get it through the line there wasn't a blockage or at least not a huge one. In case it got stuck, it would eventually dissolve.

Also, a pump's power is determined by the impeller not the motor. The motor just needs to big enough to support the impeller. To reduce the size of a pump, you need to reduce the size of the impeller. In fact, you can keep the old motor and just replace the impeller if you want to. That will reduce the flow rate, head loss and energy costs but it may not completely solve the plumbing issue although it should probably help.

Hmm, so I pursued your observation and see that there are different impellers for each power step of the maxflo pumps.
I'm guessing there's a correct velocity range for the impeller and impellers for higher power motors are longer axially to move more water.

Putting on a smaller impeller with the same motor doesn't run the impeller too fast?
Have you a reference to any curves for motor HP versus impellers versus head?
Anyway, theory aside (which for pumps I ain't got so much) sounds like you're recommending just downsizing the impeller rather than a motor change. I am also interested in minimizing pump costs at the expense of increasing run time.

If it isn't blockage, then the easiest solution would be to use smaller return eyeballs. This would increase the return head loss such that the suction would decrease.

Yeah, I was thinking about that, but, of course, that's not so energy efficient.

Thanks very much for your help Mark!