I have 2 water tanks installed in my 3 story building. 1st one is on top of the 3rd floor, the other one is on top of 2nd. The pump is installed at Ground Floor.

Before now, the water flow was manually controlled by using Ball Valves but I want to automate it using Floating valves or whatever. If I install floating valves on both tanks, the problem will be solved but the pump will blow up.

Kindly provide suitable solutions

  • 1
    Why would your pump blow up? Wouldn't you want to be clever enough to use valves that are solenoid controlled and then two float switches such that when both tanks are full the two switches cause the power to the pump to be cut off?
    – Michael Karas
    Commented Apr 30, 2017 at 9:17

2 Answers 2


The OP probably has long since satisfied his running water needs, but for anyone reading this later, here is a method to keep two tanks filled with the minimum of installed devices. The only active components required are the pump and two float switches.

two tanks no valves

Each tank must have a float switch and an overflow drain near the top.

In each tank the float switch must be set to a level lower than, but close to, the drain level.

The switches must be set to run the pump when either water level drops.

The pump must be connected to the infill of the upper tank.

The overflow of the upper tank must be connected to the infill of the lower tank.

The overflow of the lower tank should lead to a sewer or waste line via a suitable water trap.

As water is used from the upper tank, the upper float switch will trip and tun on the pump. The water in the upper tank will rise until the upper float switch is pushed off.

As water is used from the lower tank, the lower float switch will trip and turn on the punp. The water in the upper tank will rise until it reaches the overflow, then the water in the lower tank will rise until the lower float switch is pushed off.

There is no possibility of the pump running against closed valves because no flow directing valves are required nor installed.

EDIT: Another poster has installed something like this and has discovered that his drain line does not empty the upper tank as quickly as the pump fills it. His upper tank overflows before his lower tank fills.

The best mitigation for this problem is to make the drain lines very large. Since a drain should begin to operate as soon as the water level reaches it, there is almost no pressure available to drive the flow. The drain pipes should look like drain pipes, not like fill pipes.

Another mitigation is to restrict the pump flow to something the drains can handle. Either use a smaller pump, or install a gate valve or globe valve in the fill line. (Do not use a ball valve, these are hard to adjust.)

In short, to avoid flooding, you can make the drain larger or make the fill smaller.

A third way to prevent flooding is to install a second float switch in each tank to serve as a safety switch. This switch must trip at a level above the drain, and well above the fill switch, but below the top of the tank. The pump must stop when either safety switch is raised. It will start again when the drain has caught up.

  • You'll want an air-gap device on the drain line, BTW Commented Aug 6, 2017 at 23:55
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    Yes, and the drain should run where someone in the house is likely to hear it and investigate. I didn't draw the complete sewer connection because requirements for these vary widely by location. Commented Aug 7, 2017 at 0:00
  • Any number of tanks can be cascaded with this method. The operating principle is that when a tank gets low it refills itself by flooding all the upstream tanks. Commented Aug 7, 2017 at 14:14

Like Michael Karas is indicating you can an automatic floating valve on the lower tank and a float switch on the top tank. Once the lower tank is filled the valve will close and the water can continue to the top tank. As soon as the top tank is filled the level switch opens and cuts the pump solenoid switch.

Furthermore it depends on the type of pump if it blows up or not. A peristaltic pump can blows up a centrifugal pump can not. In fact the centrifugal pump starts drawing less current when pumping with no flow. No liquid transport is no required energy. Therefore less current.

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