Sump pump float switches

For the flood free basement 

A sump pump switch is designed to turn your sump pump on or off according to the water level in the sump. There are various types of float switch, the most common consisting of a microswitch that is actuated by a rod that is attached to a float - kind of like what you might find in a toilet tank. As the float rises it lifts the rod that closes the circuit at a preset height of water. The pump then starts up, and is stopped again when the float drops to a certain level.

This type of switch is not infallible, and can fail for any one of a number of reasons. One common reason is the float getting stuck between the pump and the sump wall due to the pump moving across the bottom of the sump because of operating vibrations. It can also be fouled by any debris in the sump which must be regularly cleaned. Occasionally it will just stop working for no apparent reason. In such a case, a pump motor can run continuously until it burns out, or not run at all.

The problem with float switches is there is no effective maintenance that can be carried out on them, and you just replace them when they go wrong. For this reason, many people opt for sensors; they work from the change in resistance between two electrodes fitted to the sensor as the water level rises to cover them. These, however, have their own problems and many people just stick with the tried and trusted old float switch that has remained substantially unchanged for well over half a century.

There are two basic types of float switch. There is the wide angle pump float switch that is tethered using a float cord, and the water levels at which the pump operates can be adjusted by adjusting the length of the cord. As the float rises, the cord gets tighter until it activates the switch.

Then there is the aforementioned vertical sump pump float switch, that is suitable for narrow sumps, and that operate by means of a lift rod attached to the float. The activation level with this type of switch is adjusted by moving the position of the float on the rod and adjustable stops that the float rests on.

Some float switches have a two stage design that allows two different actuation levels. The pump is actuated at the first level, and then if the water continues to rise, the second stage can be fitted to activate a visible and/or audible alarm. It can also be arranged to activate a second backup-sump pump if required.

Others simply use a second float switch attached to an alarm that is set to actuate at a level higher than that set for the pump. Then, if the pump fails to operate, the alarm will be sounded. This should be set at around two inches higher than the pump setting so that you are able to take action and carry out repairs before there is too much flooding.

The sump pump switch is an essential components of the system. Alternative types of switches are available they are all reliable. However, like many things, reliability is in the simplicity. It doesn't get much more simple than a buoyant float that actuates a set of switches.