Pool Pump Loses Prime

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  • Last Post 07 April 2020
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MannyP posted this 08 June 2016

I am wondering if someone can help me out here.  I have what appears to be an air leak that I just can't figure out. I see very small bubbles in my pump basket so I don't believe I have a major suction side air leak and no bubbles seen in my return jets. I am also not losing water.

When I turn off the pump motor, I see the water leaving my pump basket immediately.  But here is what I can't figure out.  If I start the motor again before it loses prime and I shut off the motor again after the pump basket flills up with water, the water no longer drains out of my pump basket!  It will hold prime overnight with some air pockets forming in the pump basket.

This behavior has happened a few times now.  I have replaced the pump basket o-ring and no vsisible leaks can be seen from the pump housing drain plugs. What could be going on here?

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Service posted this 08 June 2016

Hi MannyP,

I would check everything above the ground on the suction side including unions, plumbing fittings, diverter valves, pump lid, etc.. You can check this by spraying soapy water or using smoke, using either method you should see the bubble or smoke getting drawn into the leak. If you find nothing here then I would follow the Tips in this Article on How to Fix and Correct Air Leaks the article has a video and the comments have some good information as well.

I would also fully open you air release for on your filter for a few minutes even if water comes out for a while this is fine, sometimes you just need to purge all the air fully from the system.

Finally, if you could send us some photos of your plumbing that would be helpful as sometimes the way your equipment is plumbed is the culprit.

Thank You

Patrick

www.inyopools.com

Thank You

Patrick

www.inyopools.com

MannyP posted this 08 June 2016

Thanks for the reply Patrick.  I can send some photos but this is not a new pool.  The pump and filter have been working fine for years.

I don't see any visible leaks with water squirting out but I will certainly try spraying some soapy water. Wouldn't it have to be a major/visible air leak for the water to drain out of the pump basket so quickly?  And what I don't understand is why the water doesn't always drain out every time I shut off the motor.  Like I said above, it usually holds prime overnight with just some air pockets forming in the pump basket.

Service posted this 08 June 2016

Manny, you're welcome. Normally on a suction leak, you don't see water leaking anywhere as you are just drawing in air. You would see water spraying out if the leak is on the discharge side of the pump.

Go ahead and try the soapy water and check back in with the results. 

Also, I will wait for the photos.

Thank You

Patrick

www.inyopools.com

MannyP posted this 09 June 2016

Patrick, here are some photos.  Let me know if you need any other shots.  The filter is a Pentair model SMBW 4048 and the pump is an Aquatron II.  I have put some pipe sealant on the pipes to seal up any minor leaks.

Tonight, when I shut off the motor, I am losing prime more often.  I tried the soapy water spraying it all over the suction side as the water was leaving the pump basket draining back to the pool but no visible signs of it being sucked in.

I also closed all 3 suction pipe intake valves that you see in the photos here to try and keep the water in the pump basket but that didn't work.

Service posted this 09 June 2016

Hi Manny,

I think your problem are the 3 90's directly on the discharge side of the pump. Is there any way for you to eliminate some of those with 45's, flex pipe or sweep elbows. Please see the image below which shows problematic plumbing and good plumbing going in and out of the pump.

You might consider re-positioning your pump to where the broom is located in the photo. Add more straight pipe going directly into the intake of the pump this will give you some distance between the tee/cross fitting on the intake of the pump which will help. Then run flex pipe on the discharge side of the pump to the filter, the flex will allow you eliminate the majority if not all of the 90's on the discharge side, between the pump and the filter.

On a side note did you try fully purging the air in the system with the air relief valve on the filter?

Pool Pump Plumbing Schematic - Plumbing in and out pump

Thank You

Patrick

www.inyopools.com

MannyP posted this 09 June 2016

Hi Patrick.  Thanks for your input and suggestions but I'm a little confused as to why this plumbing configuration would all of a sudden be causing a problem?  It's been configured this way for a good 20 years.  Would that explain why I some times lose prime and some times I don't - because air locks are not forming in the pipe every time?  Do you think it could be an underground pipe leak? Again, I don't seem to be losing any water.

Yes, I did try and purge the air from the system but maybe I'll leave it open even longer this time.  I closed the air pressure relief valve a few seconds after water started to squirt out.

Also, I did find a very small leak on the pressure side of the filter on that straight PVC pipe going off the filter to my returns.  I taped it up with some fuse tape just to see if it would help/was the cause but I still lost prime overnight.

Service posted this 09 June 2016

Hi MannyP,

Yes, this could explain why you are only losing prime sometimes, and I don't feel it is an underground leak.

I just went through almost the identical situation on my father's pool and he did not want to mess with his plumbing, so he ended up switching out his pump to a more powerful high head pump which fixed the issue.

It could be a matter of your pump becoming less efficient or powerful over time.

Here is an article which explains How Pipe Fittings Affect your Feet of Head so the more fittings you have, the more feet of head you have. A standard pump at 30' of head would be ouputing 75 GPM where the same pump at 60' of head will be outputting 25 GPM. The same 1 HP high head pump would output 50 GPM at 60' and if you went up to 1.5 HP it would output 75 GPM at 60'. So your options would be to reduce your feet of head by re-plumbing or by going with a pump that performs better in a high head environment.

If you decide to change out the pump then I would suggest a pump like the Hayward Super II, Hayward Tri-Star or Pentair Whisperflo

Could you also let me know following:

  • What is the current HP is on your pump and the Service Factor SF, this should be on your motor label?
  • What size plumbing do you have?
  • Approximately How many feet of Pipe are running from your pump to your skimmer, if you have 2 skimmers provide distances to both.
  • Approximately how many feet of pipe are running from your pump to the main drain at the side of the pool.

Thank You

Patrick

www.inyopools.com

Thank You

Patrick

www.inyopools.com

MannyP posted this 10 June 2016

 Patrick. here are the answers to your questions:

  • What is the current HP is on your pump and the Service Factor SF, this should be on your motor label? - 1.5HP and SF=1.30 with RPM=3450
  • What size plumbing do you have? - 2 in
  • Approximately How many feet of Pipe are running from your pump to your skimmer, if you have 2 skimmers provide distances to both. - I have two skimmers - 14.5 ft and 21 ft
  • Approximately how many feet of pipe are running from your pump to the main drain at the side of the pool. - 15ft.  The pool itself is 8-10 feet deep

As I mentioned earlier, the pump is an Aquatron II.  The motor that is currently on it is an Emerson Extreme-E that was rebuilt.

Service posted this 10 June 2016

Hi Manny,

If it were me I would start with trying to make a few changes to the plumbing as outlined above, to see if this fixes your issue. If that does not fix the issue then I would upgrade to a high head pump. For your pool with the information you supplied, I would suggest this 1.5 HP Hayward Tri-Star Pump

Please keep me posted on how things turn out.

Thanks

Patrick

Thank You

Patrick

www.inyopools.com

MannyP posted this 10 June 2016

I will Patrick. Thanks for all your help.

What's the difference between the max and full rated versions of these Tri-Star pumps?

Also, should I consider a 2 speed or variable speed pump or stick with the one speed?

Service posted this 10 June 2016

Hi MannyP,

The full rated pump is more powerful than the max rated pump as the full rated pump has a higher service factor resulting in a higher True Horse Power (THP), I have laid out the math below

1.5 HP Max Rated x 1.1 Service Factor = 1.65 True HP (THP)

1.5 HP Full Rated x 1.6 Service Factor = 2.4 True HP (THP)

If you decided to go with a variable speed pump, then you will save quite a bit on your operational cost. You could set the pump on the high speed for say the first 30 minutes to get prime and then switch to a lower speed for the remainder of your filter cycle. The low speed will cost much less to operate then the high speed. If you went with a variable speed pump then I would suggest the Speck EcoMV 2.4 THP Variable Speed Pump.

Thank You

Patrick

www.inyopools.com

MannyP posted this 10 June 2016

Thanks Patrick.

In your post above, you mean the full rated pump is more powerful than the max rated pump - right?

Service posted this 10 June 2016

MannyP,

Yes you are correct, thanks for letting me know and I just edited that post.

Thank You

Patrick

www.inyopools.com

MannyP posted this 13 June 2016

Patrick, I think I may have found the issue - a drain plug on the pump housing.  

I have two drain plugs on the housing.  I replaced them one at a time testing each one and after I replaced the second one I didn't lose prime right away.  I am still seeing air pockets forming but I don't want to tighten the drain plug any more than it already is.  

I remove my motor during the winter which drains the pump basket so I don't think I need to remove that drain plug for winterization.  If that's the case, any thoughts on how to get an air tight seal around that drain plug?  Maybe some epoxy or pool putty?  Thanks. 

Service posted this 13 June 2016

MannyP,

That is great news! Most drain plugs have an o-ring does yours? If so how does it look? You may want to purchase another plug to see if a new plug does the trick, here is the AquaTron II Plug with O-ring As far as using epoxy or putty, I would be fine with anything that is not a permanent adhesive you don't want to glue the plug into the drain port.

Thanks

Patrick

Thank You

Patrick

www.inyopools.com

MannyP posted this 13 June 2016

I purchased a new drain plug at my local pool store.  It looks similar to what you have above except I believe it has a plastic washer versus an o-ring.  It held prime overnight which is much better.  

I saw some air pockets that formed in the pump basket overnight and I can see a little bit of water squirt out from the drain plug when I shut off the motor so it looks like I still have a small air leak there.

Service posted this 14 June 2016

Hi MannyP,

It may be worth trying the drain plug in my last post which uses the rubber o-ring and not the plastic washer as it would seem that the rubber o-ring would seal better.

Thank You

Patrick

www.inyopools.com

Frank7472 posted this 07 April 2020

I have a STA-RITE DURA-GLAS with a 1.65HP electric motor and a solar BADU pump rigged in paralell. For 3 months I've trying to find a solution to my electric pump losing prime overnight. I tried shaving cream, water and replacing all the seal on both pumps fliter and chlorinator lids. A combined price of about $49. What I didn't do was replace the drain plug seals. I didn't know they had o-rings. Also didn't know there are 2 plugs one on the trap where the basket sits in and one on the Volute/tank body that covers the Impeller/diffuser. I removed BOTH plug and found the lower plug seal was split in 2 and the trap seal was brittle and cracked. Changed both seals at a total cost of 4 cents and that fixed my problem and got rid of the 3months of aggavation. Hopes this helps someone. I changed the cap seal for nothing!

.Pump Set upSplit seal

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