Water level controller by monitoring water coming through tap


Joined May 19, 2020
Alternatively, we could go back to the water flow rate sensor on the output of the pump.

Turn on when the pressure before the pump rises, turn off when the flow rate after the pump falls or the tank float switch (full) is triggered.


Joined Mar 13, 2020
Automation costs money. Sensors, back flow valves, vacuum breakers - we can make it really complicated. If someone can tell me the input flow rate and the pump outflow rate, we can design a system using a "pre-tank" as mentioned with a float valve and a receiving tank float switch. If the inlet flow is just slightly more than the pump outflow rate then the only thing oscillating will be the float valve in the pre-tank. As long as more water is coming in than is going out - the float valve will keep the pump primed until water level in the pre-tank drops. Once it drops the pump can be shut off. Sort of a NAND gate setup: If the receiving tank is not full and the pre-tank is not empty then the pump runs. When either changes state the pump shuts off. Again, as long as the inlet water supply is greater than the pump outflow rate.
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Joined Feb 25, 2011
A system like this has already been suggested twice and apparently rejected. (but without the electronics)

A pressure switch seems to be the preferred way, but I still wonder what happens to the pressure when the pump is running...I predict oscillation.

My apologies , Yes I only read the resonance that cam up as I clicked the linked, not the ones I'd missed,
you dead right, this has been explained very well by others, my apologies.

Use a two tank system and float switches with a relay seems to be the way to go.
No need to apologize.
Assuming the water pipe coming into the house to the pump is a decent size, all you need is a pressure switch which responds to the pressure being on. The pump starting should only decrease the pressure slightly, so no oscillations. Then, you need a float switch in the tank to shut off the pump when tank is full. Simple solution.
Yeah, not a good idea to assume. Truth is - we don't know anything about the water supply pipe or pressure. Only thing I recall is the mention that the water pressure is not high enough to get the water to the storage tank.
Still, unless the pump turning makes the pressure go negative at the inlet, the simple solution works. Why not test this with a simple experiment before complicating the solution. Put a "T" in with a valve and see if you still get a small bit of water OUT as you crack open the valve on the T branch with the pump on!