Low Pressure Cut Off Switch Intermittently Cutting Off New Pump

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North Carolina
Thank you all for the information. I have a somewhat better understanding of the system. I can't imagine that the issue could be from lowering the water level in the well to the point of dropping the Grundfos flow rate dropping below the faucet output rate. At a head between 132' and 178' with the static water level of 40' the Grundfos output should be greater than 10gpm. Even if I ran the water for an hour straight at 4gpm (which I didn't), the head would only increase to 214'-260', at which the pump still has an output rating greater than 10 gpm. So I think the issue must be with the slow start of the Grundfos pump as Valveman stated.

The only reason I have the low pressure shut off switch is to have a failsafe in case of overdrawing the well. Since the Grundfos has integrated dry running protection I shouldn't need the shut off feature anyway. I was just being overly cautious. I will look into the Cycle Sensor as an investment for the future, but for now I'm planning to replace the switch to one that does not have a shut off feature.


Cary Austin
Staff member
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Lubbock, Texas
I don't think there is any adjustment to the Grundfos dry run protection. If I remember right it turns the pump back on every 10 minutes and pumps what little has recovered. Might be alright, but if the well is pumped dry I usually like it to recover for longer than 10 minutes.

Also, need 10 PSI less than normal air charge in the tank. Even without the low pressure kill switch there will be a hesitation in water and a water hammer thump if the tank bladder hits the bottom waiting on the 5 second start.
Hey, wait a minute.

This is awkward, but...

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