Pump loses prime and does not recover

[super_c]

Hi,

I look after a lot of pools, but only this one is giving me problems. When I connect the vacumn hose and switch the valves, the pump loses prime as expected and normally (in other pools) it comes back in a few seconds and im ready to vacumn.

With this pool, however, it loses prime and just doesnt come back. The pump is receiving water but now the pump is only half full with water.

To get around this, I have to open the pump, fill with water, turn it on, open the pump, fill with water, turn it on and so on. I can be there 40 minutes doing this.

I have a feeling its the pump, I have taken the pump apart and checked the impeller, no damage or blockages.

There is, however, a small leak, (drip, drip, drip) from the pump shell (not on a join or anything) but this does not affect the pump when it runs from the skimmer and drain lines, either together or seperately.

Any advise would be greatly appreciated.

Tom

 

[lefty51]

hello super c, welcome ! Have you inspected the strainer basket for a hairline crack. From experience I know it doesn't take much for the pump to draw air and not prime or fill up. Are there any air bubbles when it is in filter mode.? There is less resisitance when your drawing from the drains and skimmer vs a smaller vac hose. Air flows easier than water. Good luck and let us know.

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also when you shut it off, do you see water spurt out around skimmer lid ? Could be something as simple as a worn out o-ring

 

[Texas Splash]

Just to make sure, is there any chance the air could be entering from the vacuum hose or fittings when you clean this pool? I know when I vacuum, I also get more air in my skimmer basket. I don't lose prime, but it definitely drops as I believe the vacuum seal is not a "true" as the hard plumbing. Just a thought.

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Here's the TFP link for suction leaks:
Pool School - Suction Side Air Leaks

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Where are my manners? Welcome!

 

[super_c]

hello super c, welcome ! Have you inspected the strainer basket for a hairline crack. From experience I know it doesn't take much for the pump to draw air and not prime or fill up. Are there any air bubbles when it is in filter mode.? There is less resisitance when your drawing from the drains and skimmer vs a smaller vac hose. Air flows easier than water. Good luck and let us know.

- - - Updated - - -

also when you shut it off, do you see water spurt out around skimmer lid ? Could be something as simple as a worn out o-ring

Hi, thanks for your answer, ive inspected the strainer basket and all seems fine. There are not bubbles in filter mode. No water spurts out from the pump oring.

When I arrive at the pool, it is running fine with the drain and skimmers open. I just lose prime when i switch all to vacumn. Also if i switch back to normal valves, it does eventually prime but takes a long time.

- - - Updated - - -

Just to make sure, is there any chance the air could be entering from the vacuum hose or fittings when you clean this pool? I know when I vacuum, I also get more air in my skimmer basket. I don't lose prime, but it definitely drops as I believe the vacuum seal is not a "true" as the hard plumbing. Just a thought.

- - - Updated - - -

Here's the TFP link for suction leaks:
Pool School - Suction Side Air Leaks

- - - Updated - - -

Where are my manners? Welcome!

Thanks, but the whole thing, hose and vacumn is underwater when i switch the valves over, so im guessing no air, plus i use the same hose on other pools and this is the only pool i have issues with.

 

[TomBorg]

Last year I had a bad valve that was allowing air to be sucked in right where the handle protruded. It wasn't a problem at normal pressure, but when when vacuuming, the increased suction allowed it to pull in dramatically more air. If you can put your ear up to the valves, you might be able to hear if this is your problem. Or you can do the shaving cream test on all the valves and visible joins.

If there is a hairline crack in one of the pipes underground, it can suck in air through the soil.

 

[super_c]

Last year I had a bad valve that was allowing air to be sucked in right where the handle protruded. It wasn't a problem at normal pressure, but when when vacuuming, the increased suction allowed it to pull in dramatically more air. If you can put your ear up to the valves, you might be able to hear if this is your problem. Or you can do the shaving cream test on all the valves and visible joins.

If there is a hairline crack in one of the pipes underground, it can suck in air through the soil.

Thanks for your reply, shaving cream test?

 

[Texas Splash]

Some people find the shaving cream test easy to spread over joints, pipes, and such to see if it gets sucked "into" a crack or bad seal for parts you can see on the surface. Another method is to take a hose and let water flow over the parts to see if the air bubbles go away - just like submerging the crack or bad seal.

 

[lefty51]

Last year I had a bad valve that was allowing air to be sucked in right where the handle protruded. It wasn't a problem at normal pressure, but when when vacuuming, the increased suction allowed it to pull in dramatically more air. If you can put your ear up to the valves, you might be able to hear if this is your problem. Or you can do the shaving cream test on all the valves and visible joins.

If there is a hairline crack in one of the pipes underground, it can suck in air through the soil.

I had the exact same problem with a jandy valve, one of the retaining screws was stripped out and wouldn't tighten enough to seal. Was only apparent in high suction situations. good call