Automatic Water Pumps and the Different Switches

Once turned on at the mains, an automatic water pump will turn itself on or off as the water level rises or falls. Automatic pumps are very useful in projects as they are often only seen twice in their life, once when installed – and eventually when they are removed for replacement.

Automatic Pumps are Available with Different Styles of Float Switches

There are 3 main types of automatic switches available:

• Pendant float switch
• Tube float switch
• Sensor panel

The diagram below compares a manual pump, with two automatic pumps, one with a pendant float switch, and one with a tube float switch.

Pendant Float Switch

Pendant float switch pumps have a paddle like float attached to them. These work on pretty much the same premise at the ball cock system in a typical toilet.

The float hangs down at the side of the pump, when the water rises, the float rises along with it. Once the water reaches a certain height the float reaches its ‘on’ position, which then turns the pump on and begins to pump the water away. When the water lowers, the float lowers back down to the ‘off’ position this turns the pump back off again.

These type of pendant floats are not ideal for every situation due to the clear area they need around the pump so that they do not snag or catch on any obstacles stopping them from working. The diagram above shows how this can be an issue in narrow chambers.

This system does not offer exact depths at which the pump will turn on or off.

Tube Float Switch

These pumps are designed for tight spaces, such as sumps or narrow chambers. Examples include the Tsurumi POMA Submersible Automatic Sump Pump (pictured left).

Unlike the pendant float switch that dangles from the pump and sits on the surface of the water, the tube float is exactly that, it is a tube attached to the pump with a small float inside. When the water surrounds and raises around the pump, the ball float inside the tube raises with the water turning the pump on, when the water level falls the float drops along with it turning the pump off.

This prevents the float switch from fouling or becoming stuck on a chamber, as the diagram shows. They also have an on and off level provided, so you know when the pump will be activated.

Sensor Panel

There are a few pumps available which a sensor panel built on to the side of the pump housing, or in a separate panel. These can be used when the on or off position needs to be much lower, and more accurate than a standard paddle float can provide.

An example is the APP RS32EA Submersible Puddle Pump (pictured right). A fixed panel it is ideal in enclosed spaces and where minimum water levels are required. These can pump the water away to an accurate required depth to the nearest milometer.

These are more expensive than pendant float switches due to the more complex electronics involved.

Automatic pumps are designed to turn on and off when needed automatically, so choosing the correct pump with the best suited float switch is very important. If the wrong pump is selected for the wrong environment, it could cause the pump to stop working.

You will find that manual pumps usually pump to a lower level than the automatic version, but the manual models require supervision, where as the auto models can be installed in to sumps and left to do the job they are needed without being monitored.

The EGO 500 Submersible Puddle Pump is very popular as this is the only pump we have available that can be swapped between manual and automatic modes.