Why it's not okay to connect two float switches for two tanks directly to a single phase motor

Thread Starter


Joined Nov 9, 2022
I want to connect two float switches to two tanks, one of the tanks is over head the other and I want to directly connect the float switches to a single phase motor using just the on/off switch. I feel there is no need to construct a panel which will have a contactor, relay and other stuffs. Hope it's fine Ryt?


Joined Nov 6, 2012
Of course it could be a very dangerous Shock-Hazard depending on the
particular "Float-Switches" being used, and various other wiring details.

Pictures are worth a thousand words.


Joined Mar 19, 2019
Your largest problem will be the lack of deadband. In other words, the switch will be chattering at the level setpoint as it senses minute changes in level, ripple for example, and is constantly turning the motor on and off trying to control. You want the switch to turn on/off slightly above and below the setpoint. The Square D company sell quite a bit of level control products and looking at how they are designed to work may give you some ideas. You failed to mention whether you are controlling the filling or emptying of the vessel.


Joined Sep 17, 2013
Apart from the pump(s) you will also need valves: otherwise the top tank could simply empty into the bottom tank if their plumbing is interconnected..


Joined Jan 15, 2015
Why it's not okay to connect two float switches for two tanks directly to a single phase motor

It's not OK unless your float switches can handle your pump motor current. I have no idea how you plan to actually wire this project or your goal is with this project. This is why a drawing or schematic of your game plan with your goals would come in handy so until then I guess it is OK or not OK.



Joined Jan 23, 2018
Accessory float switches are available for sump pumps. They are totally insulated and pose no shock hazard, and they have several inches of dead band so there is never any chattering.
Of course since no hint is provided as to how the levels in the two tanks are related or even how the motor will affect the levels, I am not going to suggest the obvious scheme that has been used elsewhere, in the past, and has worked very well.
It worked on a dairy farm and kept the water levels for the milk-can-cooling water tank and the livestock drinking water supply tank at the appropriate levels very well.
Would it apply in the TS application? Possibly.