Trouble Priming higher-than-water pump

gdo

Well-known member
Apr 26, 2022
66
Orange County
My pool has a basin that is used as part of an autofill mechanism: the pump pulls water from the basin and re-injects it into the pool, which then spills it back into the basin.

Pool_and_basin.jpg

As the pool water evaporates, this cycle makes the level in the basin drop because the water from the basin is used to fill out the missing water in the pool until it reaches the edge where it can flow into the basin again. Lowering the level in the basin triggers my autofill valve to ensure the basin never runs out of water, and that's how refill works.

I got into a situation where the basin _did_ run out of water (you can get to that point when you start the pump after it hasn't run for a while and (a) the basin doesn't have enough water to completely replace the evaporated water in the pool and (b) the autofill valve can't keep up with the pump).

Now the pump won't prime anymore. The pump is about 30 ft from the pool and 6 ft higher. It's a Pentair VSP, and I've left it in "priming" mode for 11 minutes, which is the default setting for that pump. During this time, I did see bubbles come out on the return side into the pool, so the pump is moving air (which I assume also means that water is coming up the suction line) but after 11 minutes of bubbling, the pump shut down and the flow had still not been established.

I've tried to remove the left-side check valve to fill out the suction side with water, hoping there would be another check valve at the bottom that would let the water accumulate in the pipe, but that didn't work, and I suspect all I was doing was to fill up the basin through the drains.

I encountered a similar problem with one of my fountains and it turns out that a coordinated start process with an assistant worked: the assistant plugged the drain with her hand while I filled up the suction side and the pump basket, and then she removed her hand as I started the pump.

I suspect I can do the same here, but there are 4 drains with anti-entrapment covers to plug, so I would need quite a few assistants!

Surely there's a simpler way?

I'm tempted to let the pump try to prime for 30 minutes, as the manual explicitly calls that as the maximum priming time allowed (that's the max that you can set it to as well in the user interface). Makes sense to try?

Thanks in advance!
 
Does the pump have unions? See if the inlet one is loose or damaged. Also, check the inlet plumbing by grasping the pipe and trying to move it from side-to-side. If it is loose it can be sealed with silicone sealant for a temporary repair, but at a 6' lift, you need a more permanent repair that might include replacing the inlet plumbing with a hi-temp union. Also, a pump that runs dry can/will damage the shaft seal and that can prevent it priming, especially at that height.

Has the drain plug on the pot come loose or need to be resealed.

What type of check valve in front of the pump? If a Jandy-type, be sure the lid O ring is good and lubed. If a union type, be sure the O rings are lubed and the fittings tight.

A pump that far from the pool and that high above the water means that everything has to be better than just OK for it to prime.
 
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A 6ft lift can be a headache. If everything is sealed properly and the intake check valve is in good working order, it may take a dozen times of filling pot with water, run for a minute and repeat. Try and work the water up the intake. If not a plugs and drain king bladder or you can wrap a rag around the end of a garden hose(electric tape helps) to make somewhat of a seal and stick it in the MD with the others plugged.
 
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AS others have said, all your seals have to be close to perfect for the pump to lift 6 feet to get the prime started.

Long term fix would be to lower the pump if that's possible.
 
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full
 
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