Chronic prime issues: "extended pot reservoir"?

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austin7537
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My Pool: 15K gallons, negative edge and in-floor cleaner, 3 pentair whisperflow pumps (main, cleaner, and catch basin).

Chronic prime issues: "extended pot reservoir"?

Postby austin7537 » Sun 16 Sep, 2018 12:51

The water intake for my negative/infinity edge catch basin is waaay below my pump, maybe 10ft. The pool installers warned me that this would lead to difficulty priming and they were right. There's a lot of negative pressure due to the height so the slightest leak (like when the pump lid o-ring has a piece of grass or something in it) causes a loss of prime overnight, and it's a real pain. I have to go through the priming cycle (pump off, fill the bucket, lid on, pump on, repeat) well over a dozen times.

I know there's no 100% solution to avoid losing prime, other than keeping the pump running 24/7, but hoping there's a technical solution to restore prime more easily.

I think I could get the pump to prime in one or two shots if only I had a larger bucket/pot reservoir on the pump. That is it could hold more water pre-impeller, to get more of a vacuum going when trying to prime. So it feels like what I need is some sort of extender that sits on top of the pot, or a separate reservoir that I can plumb in between the pump pot and the check valve.

So my questions is do you have any tips on what I should look to buy here? I can't find a product that directly extends the existing pot (Pentair Whisperflow), but I can buy a separate pump trap assembly. Do you think that would work?

Thanks everyone!

Keith


Denniswiseman
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Re: Chronic prime issues: "extended pot reservoir"?

Postby Denniswiseman » Sun 16 Sep, 2018 16:34

Try placing a check valve on the suction side to the pump to keep the suction line permantly charged probably as low as possible so that when you prime throught the pump, the water fills the line and you don't have to spend ages priming
Also is it possible to place the pump at a lower level
austin7537
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Posts: 5
Joined: Sun 16 Sep, 2018 12:24
My Pool: 15K gallons, negative edge and in-floor cleaner, 3 pentair whisperflow pumps (main, cleaner, and catch basin).

Re: Chronic prime issues: "extended pot reservoir"?

Postby austin7537 » Sun 16 Sep, 2018 20:40

Good suggestion, but before the pump on suction side, there's 3 or 4ft of exposed pipe with a check valve, then 30-40ft horizontal & 10ft vertical to the catch basin, all under ground and concrete. Once air gets in around the pump, it easily gets through the check value ... there's a lot of water in the pipe pulling it through. The only install point I'd have access to would be in the catch basin itself. Maybe if there was some sort of one-way valve I could install at the intake on the floor of the catch basin that would work?
Denniswiseman
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Re: Chronic prime issues: "extended pot reservoir"?

Postby Denniswiseman » Mon 17 Sep, 2018 02:12

The check valve is a one way valve, designed to prevent reverse circulation, yours may be faulty
If the only problem is when you work on the pump then an ordinary on/off valve in the line would suffice
austin7537
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Joined: Sun 16 Sep, 2018 12:24
My Pool: 15K gallons, negative edge and in-floor cleaner, 3 pentair whisperflow pumps (main, cleaner, and catch basin).

Re: Chronic prime issues: "extended pot reservoir"?

Postby austin7537 » Mon 17 Sep, 2018 09:42

I don't think the check valve is faulty, it's not not designed to hold back reverse flow of air for long periods, especially when there's a hundred or so pounds of negative water pressure pulling on it. I hadn't thought of using a valve, could plumb in a jandy and tie it to pump operation. Good suggestion, thanks!
Denniswiseman
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My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Chronic prime issues: "extended pot reservoir"?

Postby Denniswiseman » Mon 17 Sep, 2018 10:01

I think your calculation of a 100 or so pounds of negative pressure is quiet a bit off
1 vertical foot head of water is 0.434 lbs sq in. so if there is about 10ft head (0.434 x 10) = 4.34 lbs negative pressure
There are different types of NRV's some are a flap type and some are spring loaded which with a negative pressure will pull closed
austin7537
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Posts: 5
Joined: Sun 16 Sep, 2018 12:24
My Pool: 15K gallons, negative edge and in-floor cleaner, 3 pentair whisperflow pumps (main, cleaner, and catch basin).

Re: Chronic prime issues: "extended pot reservoir"?

Postby austin7537 » Mon 17 Sep, 2018 11:20

Haha yeah it's way off, I was guesstimating the weight of water in the entire pipe but yes it should only be head. It's 2" pipe, so pi x (2/2)^2 = 3.14 sq in and 3.14 x .434 x 10ft = 13.6 lbs negative pressure. This is my current flapper NRV: https://www.amazon.com/gp/product/B0039PXC8K/

I had another idea. Currently the check valve is horizontal at the same level as the pump, which means that any air penetrating the pump is pretty much right at the valve. I could instead plumb the check valve vertically, with an upside down U between it and the pump (I'm sure there's a technical term for that!). The theory is that there would always be water above the check valve, even if I had the pump pot open for basket cleaning, etc. Think that would help? Alternatively I could just look for a most robust NRV.
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Re: Chronic prime issues: "extended pot reservoir"?

Postby Teapot » Mon 17 Sep, 2018 11:30

Mount your pump lower or use a submersible pump.
Denniswiseman
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Re: Chronic prime issues: "extended pot reservoir"?

Postby Denniswiseman » Mon 17 Sep, 2018 12:17

austin7537 wrote:Haha yeah it's way off, I was guesstimating the weight of water in the entire pipe but yes it should only be head. It's 2" pipe, so pi x (2/2)^2 = 3.14 sq in and 3.14 x .434 x 10ft = 13.6 lbs negative pressure. This is my current flapper NRV: https://www.amazon.com/gp/product/B0039PXC8K/

I had another idea. Currently the check valve is horizontal at the same level as the pump, which means that any air penetrating the pump is pretty much right at the valve. I could instead plumb the check valve vertically, with an upside down U between it and the pump (I'm sure there's a technical term for that!). The theory is that there would always be water above the check valve, even if I had the pump pot open for basket cleaning, etc. Think that would help? Alternatively I could just look for a most robust NRV.

That calculation gives you the total area pressure not PSI
The fact that it is a flapper type horizontal at a high level would easily allow to drain back some
Try testing a spring return NRV by trying to blow back through it
austin7537
I'm new here
I'm new here
Posts: 5
Joined: Sun 16 Sep, 2018 12:24
My Pool: 15K gallons, negative edge and in-floor cleaner, 3 pentair whisperflow pumps (main, cleaner, and catch basin).

Re: Chronic prime issues: "extended pot reservoir"?

Postby austin7537 » Mon 17 Sep, 2018 17:42

Denniswiseman wrote:That calculation gives you the total area pressure not PSI
The fact that it is a flapper type horizontal at a high level would easily allow to drain back some
Try testing a spring return NRV by trying to blow back through it


Thanks for all your help Dennis! I'm going to plumb in a spring NRV on the vertical below the pump, will report results back here.

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