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Water flow switch

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New Member
I am looking for a simple solution to something I know nothing about.

Please forgive a newbie if this is the wrong forum to post this kind of very basic questions.

To protect the water pump, I want to install a flow sensor that turns power off to the pump if there is no water (which happens often here in Panama).

I found these switches


But I have no idea how to get that signal to switch the 110Volts for the pump.

All I found is this, but unsure if that would solve my problem


Would that work with a flow switch?

Or maybe there is another simple solution. Any help is appreciated.

Ian Rogers

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Most Helpful Member
looks like a 12v switch with a maximum 15mA current... A simple 12v 5 pole relay will switch the 110v .. All you need is a AC/DC convertor ( wallwart ) or we call a "12vdc mains adapter" and use the switch to drive the relay..


Well-Known Member
you could use the flow switch but it looks like it needs a controller too....

easiest solution is a sump pump float switch if you can use that


Well-Known Member
Where is the pump suction connected to ?
Is it to the street mains ? (illegal) or is it from a reservoir filled by the street mains ?
If a reservoir; a paddle pushed by the water inflow at the filling pipe can turn off the pump when there is no flow.
To protect the water pump, I want to install a flow sensor that turns power off to the pump if there is no water (which happens often here in Panama).
That is not right. "if there is no water" where? In the reservoir ?
"There is no water" is not "there is no flow"
Where is the flow you want to detect ? At the pump outlet or the reservoir inlet ?
Water can be flowing into a nearly empty reservoir with too low level to be pumped.
The correct way is to use a float switch in the reservoir that will disable the pump when level is too low.



New Member
Thank you very much for the replies. Externet, you saved me!

I did not know it was illegal to connect pump suction to the mains. Now that I googled the reason, it makes perfect sense.

Having the need for a tank changes everything. And your solution makes perfect sense

Thanks again.


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Most Helpful Member
To protect the water pump
I pull water out of the ground and store it in a tank for use later. This switch measures the pressure at the tank and turns the pump on if the pressure is below 30 and turns off the pump if the pressure is above 50 pounds.
If the ground water is gone the pump runs dry and burns up. "Water Pressure Switch - 30/50 psi with Low Pressure Cut Off" This switch is like the first one (on at 30, off at 50) but it has a "low pressure cut off" function. If there is no water, the pressure drops below 10 and the power is turned off. There is a lever on the right side. To start you must push by hand and hold until the pressure gets above 10, then release and leave. If the water is all gone the pressure is below 10 and the switch will stop and wait for you to start the pump again.
This is what I am using. I also use a "float switch" like in post #4.
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