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Old 11-03-2022, 12:39   #1
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Jabsco water pump with bypass valve cycling too much

A few months ago I replaced a Jabsco 2GPM pump with a 3GPM pump with integrated bypass valve. This was done in an attempt to stop the pump from cycling so much, as I had tried adding an accumulator to the 2GPM pump and it still cycled too much.

The 3GPM pump still cycles on/off about every 1 second, this is with the accumulator still installed in the system. I really thought the bypass valve would almost eliminate the cycling, it came with no instructions.

According to online literature no accumulator is necessary, I thought it wouldn't hurt, but do I need to remove that to make the pump work correctly?
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Old 11-03-2022, 22:02   #2
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Re: Jabsco water pump with bypass valve cycling too much

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Originally Posted by sailingunity View Post
A few months ago I replaced a Jabsco 2GPM pump with a 3GPM pump with integrated bypass valve. This was done in an attempt to stop the pump from cycling so much, as I had tried adding an accumulator to the 2GPM pump and it still cycled too much.

The 3GPM pump still cycles on/off about every 1 second, this is with the accumulator still installed in the system. I really thought the bypass valve would almost eliminate the cycling, it came with no instructions.

According to online literature no accumulator is necessary, I thought it wouldn't hurt, but do I need to remove that to make the pump work correctly?
You didn't specify what kind of accumulator tank you have.
Some of the little plastic ones are hardly more than a pulsation/water hammer dampener.
The better ones use a diaphragm/bellows/bladder, whatever, to separate the air/water sections.
Over time, in a tank without that separation the air charge will dissolve into the water and disappear.
Success with an accumulator relies upon a static air pressure charge that is ~1/2 the psi of the shut-off point of the pump.
Even the best tanks over time can leak their air charge out thru the Schrader valve, so it's something to monitor from time to time.
Some of the pressure switches that are built-in to pumps have too close of a setting between on/off.
Best results are obtained with a remote switch like a "Square D" or "Furnas", where the cut in/cut out pressures are adjustable.
The "Bypass valve" is just a tiny passage/device, connecting the inlet and outlet together that "dumps" the pressure behind the outlet valve in the pump so that when the pump comes on it doesn't have to start against the cut-out pressure, it's similar to an "Unloader valve" in an air compressor.
The pumps that advertise "No accumulator tank necessary" are by design made to cycle endlessly, they must, as water won't compress.
But, set-up properly they work just fine with a tank, at least the Flo-Jet and Shure-Flow ones I've installed did.
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Old 13-03-2022, 02:07   #3
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Re: Jabsco water pump with bypass valve cycling too much

The pumps with the pressure switch in the front have a simple micro switch that doesn't have much range between on and off pressures. As Bowdrie said, most people bypass the stock pressure switch and use a water pressure switch like the one shown. The on and off pressures can be set separately. Most come set at 20/40psi but can be reset.
About $12 on ebay or Amazon.
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Old 13-03-2022, 18:17   #4
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Re: Jabsco water pump with bypass valve cycling too much

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Originally Posted by Lepke View Post
The pumps with the pressure switch in the front have a simple micro switch that doesn't have much range between on and off pressures. As Bowdrie said, most people bypass the stock pressure switch and use a water pressure switch like the one shown. The on and off pressures can be set separately. Most come set at 20/40psi but can be reset.
About $12 on ebay or Amazon.
Interesting and thanks for sharing. I'm familiar with that type of switch as it's what comes on a typical water well.

Strangely, I moved the pump this weekend from the engine room to under the sink - which I figured would improve the flow (much shorter run), but instead things have gotten much worse. Specifically, the pump waits a long time to turn on when a tap is opened, and it'll give like 4 spurts of pressure, then it waits another 10 seconds before turning on. I speculate this is a symptom of sucking area in before the pressure switch.
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Old 14-03-2022, 05:47   #5
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Re: Jabsco water pump with bypass valve cycling too much

I have a pump with integrated bypass switch and got rid of my accumulator. Mine has an Allen wrench adjustment on the pressure bypass switch so I was able to adjust so it runs continuously with any water flowing and stops soon after faucet is closed. Sounds like your pressure is set too high if its cycling like that
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