Variable speed pump losing prime

elmorage

Well-known member
Jun 21, 2013
45
NY
We have a new inground pool, less than 36 hours old. Our variable speed pump seems to be losing prime as the water level in the pump strainer gets noticeably lower throughout the day. We mentioned it to our pool builder and he said the variable speed pumps run differently and aren’t always totally full to the window because it isn’t always running with full suction. It made sense at the time but we are seeing the water sometimes get almost as low as the intake hole. Is this normal or is something wrong?
 

ajw22

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TFP Guide
Jul 21, 2013
8,822
Northern NJ
What speed are you running the pump?

Do you have a variable speed pump or a dual speed pump that you signature says?

VS pumps often develop an air bubble in the pump basket when run at low speeds. Does the air bubble decrease if you increase the RPMs?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,950
Bedford, TX
E,

While it is true that most VS pumps have a little air in the very top of the pump lid, it should not increase as the day goes on.

Normally this is a sign of a very small suction air leak. The very first place to look would be the pump lid O-Ring.. I would make sure the O-Ring is well lubed with pool-lube.

Edit... I wrote the above and then realized that you have a two-speed pump, not a variable speed pump...

Either way, the air under the pump lid should not increase as the day goes on... Your pool builder needs to fix it.

Thanks,

Jim R.
 

elmorage

Well-known member
Jun 21, 2013
45
NY
It is variable speed, I forgot to update my signature. We run at speed 3 in the am for the heater, speed 2 during the day, and 3 again in the evenings to mix in the after dinner bleach.

It is not a small air bubble, it is a good 2-3 inches of empty space and below the strainer basket but barely above the suction intake.
 

elmorage

Well-known member
Jun 21, 2013
45
NY
All four speeds are still the Hayward presets, 1150 1725 2300 2875.

I just ran it on speed 4 and the basket filled all the way to the lid.
 

Jimrahbe

Mod Squad
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Jul 7, 2014
13,950
Bedford, TX
E,

The key to me is does the bubble get bigger as the day goes on. I believe that a bubble is normal for any VS pump running at a low speed, but it should not get bigger.

I have three IntelliFlo pumps that run 24/7 at 1200 most of the time.. All three have some bubbles under the lid, but on all three of them the bubbles never get any bigger. They run for months with the same bubbles. If your bubble grows in one day, then I can't possibly see how that can be normal operation or how the pump was designed.

Thanks,

Jim R.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
8,822
Northern NJ
Almost sounds like you dont have enough water coming in. Have you tried a lower speed?
Actually it is the reverse. The pump is sucking in enough water for the set rpm flow. That is not enough to fill the pump basket. At full rpm the water flow volume is sufficient to fill the pump basket.
 

Jimrahbe

Mod Squad
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Jul 7, 2014
13,950
Bedford, TX
Jim, have you ever run your pumps at speeds of 600 rpm?
PM,

The main reason that I use 1200 RPM is that is where I get good skimming and my SWCG's flow switch is closed.. For me personally, running anything below a 1000 RPM just does not make much sense.. I see no reason to run the pump if you are not skimming and making chlorine.

The OP in this thread is running 1750 or higher, so we are not really taking about a very slow RPM...

Thanks,

Jim R.
 

markayash

Gold Supporter
Mar 21, 2016
549
Marrietta Ga
Actually it is the reverse. The pump is sucking in enough water for the set rpm flow. That is not enough to fill the pump basket. At full rpm the water flow volume is sufficient to fill the pump basket.
Interesting, any chance a air leak before the pump? They are hard to spot when the pump is running but sometimes get damp when pump is off. I have 4 inputs and had one 90 I forgot to glue.
 

elmorage

Well-known member
Jun 21, 2013
45
NY
Interesting, any chance a air leak before the pump? They are hard to spot when the pump is running but sometimes get damp when pump is off. I have 4 inputs and had one 90 I forgot to glue.
Wouldn’t know, plumbing is buried under 3 feet of pea gravel.
 
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Reactions: markayash

elmorage

Well-known member
Jun 21, 2013
45
NY
Is the pump really losing prime and stop flowing water or is it just a visible air bubble?
Air bubble doesn’t really describe it, its a good 2-3 inches of empty space but water is still flowing and no air is coming through the returns.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
8,822
Northern NJ
Air bubble doesn’t really describe it, its a good 2-3 inches of empty space but water is still flowing and no air is coming through the returns.

If water is flowing and no air is coming through returns it sounds normal to me.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,950
Bedford, TX
E,

The key is does it get worse as the day goes on??? If it does not get worse, then I see no reason to worry about it..

Jim R.