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Discuss Water pump start-stop every second in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Hi guys,

I have installed a Nordstrand 90W water pump with flow switch, which you can find on eBay and Amazon. It worked brilliantly when I first installed it, and it still provides excellent flow rate through the taps.

But it has started doing this weird thing: when I turn the tap off, the pump stops and starts about once every second. I'm fairly sure it's the flow switch that is sending the start-stop signals, but I don't know why or what to do about it.

The only way I have found to stop this is to turn the pump off, and then when I turn it back on it doesn't do it until the next time I open and close a tap. I have checked the pipework and I don't think there is a leak anywhere, so the flow switch is not detecting actual flow.

Any ideas what it could be and how I could fix it? Thanks
 
A

Aire

Sounds like you need some non return valves just after the pump outlet.
 
A

Aire

Why now, they weren`t they required at installation and it has been working fine. I`m more inclined to think sticking flow switch.
Maybe so, although op failed to mention when the pump was installed. It may have been installed last week and now having an issue, I've had a few instances where pumps have worked fine for a couple of weeks after install and then began pulsing requiring non return valves to be fitted.
 

rpm

Esteemed
Plumber
Maybe so, although op failed to mention when the pump was installed. It may have been installed last week and now having an issue, I've had a few instances where pumps have worked fine for a couple of weeks after install and then began pulsing requiring non return valves to be fitted.
Interesting, anyone else experienced this and know why it happens? Only asking as baffled as to why.
 
A

Aire

Interesting, anyone else experienced this and know why it happens? Only asking as baffled as to why.
Depends how the pump is piped, if the outlet has a vertical rise on it, you can find that after the pump stops, as the water falls back down it activates the flow switch, which pumps the water back up and then shuts off, water falls back down and so on
 
There was a "Shower Power Booster Pump" on a thread here recently that had a similar type pump of lower power with flow switch problems that was cured by the addition of a filter, it had been caused by debris in its NRV.
 
Last edited:
Installed a check valve after the flow switch and that has fixed the problem, cheers guys

I suppose it must have been the depressurisation after the tap closing, causing backflow through the flow switch, that turned the pump on to repressurise and turn off, rinse and repeat. Valve prevents backflow. Don't know why I didn't think of that before ;)
 

rpm

Esteemed
Plumber
Installed a check valve after the flow switch and that has fixed the problem, cheers guys

I suppose it must have been the depressurisation after the tap closing, causing backflow through the flow switch, that turned the pump on to repressurise and turn off, rinse and repeat. Valve prevents backflow. Don't know why I didn't think of that before ;)
How long has the pump been installed and working correctly?
 
Pump has been installed for a couple of weeks, but I don't think there has been any proper usage to test it as other work has been going on, I just came back to this the other day and noticed the problem. Glad it's sorted, one less job to worry about
 

rpm

Esteemed
Plumber
New and being basically unused changes things somewhat from old and new problem.
 

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