What Is a Float Pump?

What Is a Float Pump?

A float pump is a pump that automatically turns on when the water level rises to a preset height. Float switches are used for a variety of tank, rainwater, wastewater and sewage applications.

They work by using internal switches that open or close, depending on the liquid level. They are the most reliable and cost effective way to control a sump pump system.


The performance of any pump can be described in terms of its ability to raise or lower a liquid. The quantity measured is called head and it is a function of both the volumetric flow rate of the pump and its inlet pressure (or suction feet or meters of head).

Different types of pumps use different methods to impart energy to the liquid but they all work by adding velocity, compression or both. Pumps are commonly rated for their horsepower, volumetric flow rate and head.

The most reliable and advanced float switches are electronic. They feature piggy-back plugs that allow you to simply plug them into a power outlet and then plug your pump directly into the back of the switch. They also have almost no moving parts and can withstand much higher amounts of current than other float switches. Using an electronic switch with a pump of a lower horsepower rating can shorten its life.

Float switches

A float switch is an electronic device that monitors the liquid level in a tank or container. It uses a magnet and reed switch that connect to complete an electrical circuit. Rising liquid levels move the float up and down, and this movement causes the switch to activate. This switch can turn on pumps, alarms, and other electronic devices.

There are three types of float switches: tethered, vertical action, and diaphragm. A tethered switch has a floating hollow body with a steel ball inside that lowers or rises as water level changes. When the internal switch in a tethered switch activates, it will trigger the pump to start.

A vertical action float switch has a sensor that sits in the bottom of a tank and moves up or down as the liquid level rises or drops. This is the most common float switch found in sump and sewage pits. These floats are less expensive than tethered switches but have the same operational mechanisms.


Every three to five months, a homeowner should perform a quick test of the sump pump. By pouring water into the pit and watching as the float rises, you can confirm that it works as it should.

If the float switch doesn’t respond to rising and falling levels of water in the pit, it may need a mechanical repair. It also may need to be replaced entirely.

Check the owner’s manual to see if the pump bearings need lubrication. A lubrication kit is typically included with the unit.

In addition, you can check that the power cord is plugged in properly and that there are no broken or tangled pieces of wire. You can also inspect the pump pit to make sure nothing has been deposited there that could block the float or prevent it from raising and lowering properly. You should also remove anything that has collected in the basin, as it can cause a build-up of grime that interferes with operation.


There are a variety of reasons why your pump’s float switch may not be working. Fortunately, the majority of these problems can be fixed fairly easily.

Check that the pump is plugged in properly, with no exposed wires and no visible signs of corrosion or damage. Make sure that it is plugged into its own electrical outlet and not sharing a circuit with any other outlets or appliances.

Test that the pump runs correctly by plugging it directly into an outlet (without using the piggyback plug attached to the float switch) and seeing if the breaker or fuse pops. If it does, the float switch is likely not functioning properly and should be replaced.

Visually inspect the float switch to see if it is able to move up and down freely in the sump pit. Sometimes, it can become blocked by mineral/dirt buildup that needs to be soaked away, and in other cases, the switch can need to be adjusted – follow your owner’s manual for instructions on how to do this safely.

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