Automatic water pumps are highly popular. Once switched on at the mains, an automatic pump turns itself on and off as the water level rises and falls, reducing the need for human intervention. In many projects they are only seen twice in their life, once when installed and again when eventually replaced, with perhaps some minor servicing in between. That makes them ideal for a passive system in basements, sumps or chambers where the water level is not monitored by hand.
The different types of automatic pump switch
Automatic pumps come with different styles of switch, each suited to different spaces and requirements. The main types are the pendant float switch, the tube float switch, the arm float switch, and sensor or panel control. Below is how each works and where it is best used. The diagram 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, working in a similar way to a ballcock in a toilet cistern. The float hangs beside the pump and lifts as the water rises. When it reaches a certain height it triggers the pump on, and when the level drops the float lowers and switches it off. Simple and effective, but pendant floats are not ideal for tight spaces: they need clear room so the float does not snag, and they give an approximate activation range rather than exact on and off levels.
Tube float switch
Tube float switch pumps are designed for narrow or confined spaces such as sumps or small chambers, and for when the on or off position needs to be much lower and more accurate than a pendant float allows. An example is the Tsurumi POMA submersible automatic sump pump. Instead of a float hanging externally, a small float ball is enclosed in a vertical tube on the pump. As the water rises the internal float moves up and switches the pump on, and as it falls the pump turns off. Because the float is housed inside the tube it is less likely to foul against chamber walls, a big advantage in confined setups, and it gives a defined on and off level. See our Tsurumi pumps.
Arm float switch
Used in similar situations to tube float switches, some pumps have a float switch on an arm. These suit tight or narrow setups such as a small chamber and give a set on and off level. The arm can be more exposed to snagging on cables, but is less prone to blockage than a tube float, which makes it a popular choice. The AMA Drainer 301, pictured below with an arm float switch in our FPS Iguazu Sump 635 packaged pump station, is a best seller and a firm favourite. We explain its popularity in why the AMA Drainer 301 is so popular.
Sensors and panels
Some pumps use a sensor panel built into the housing or connected via a separate control unit, used where the water level needs more precise control than a float switch allows. A good example is the APP RS32EA submersible puddle pump, which has a fixed panel that pumps water down to low levels accurately. Another is the Tsurumi LSC1.4S, which can be fitted with sensor probes or supplied with a control panel for fixed installations such as lift shafts.
See the Tsurumi LSC with sensor and extension probes:
Sensor panels are particularly useful in enclosed spaces or where you need the pump to remove very shallow water. Because of the electronics involved they are typically more expensive than float switch models, but they offer higher precision and reliability.
Separate floor-level sensor
A newer option is a sensor that sits flat on the floor on its own lead rather than on the pump, as used by the Stream SPP2-4A and SPK530A and the EVAK Residox Crab sensor. Because there is no float to lift, the pump can start and stop at a much shallower depth. Our guide to pumping water away automatically at floor level explains how it works.
Choosing the right type
Selecting the right switch for your environment matters. The wrong type may not function correctly: a pendant float could snag in a small sump, or you may need the pump to start at a lower level than the float allows. It is also worth noting that manual pumps generally pump down to slightly lower levels than automatic ones, but they need supervision, whereas automatic pumps can be installed and left to manage themselves, which suits most long-term setups. For more on choosing for a cellar, see our guide to the best automatic water pump for a flooded basement and how to pump water away automatically at floor level. You can also browse float switches and accessories.
A versatile option: the EGO 500
One of the most popular models is the EGO 500 submersible puddle pump, which switches between manual and automatic modes. In automatic mode it pumps down to 60mm before switching off, helping maintain a low water level; in manual mode it can pump as low as 10mm. The AMA Drainer 301 can also switch between modes, though it is predominantly used as an automatic model. The EGO 500 SELS in the same range uses adjustable sensor probes instead of a float.
Video guide: the different types of float switch
Final thoughts
Automatic pumps save time, reduce stress, run sewage systems effectively and make flood prevention more reliable. Whether you choose a pendant, tube, arm or sensor panel switch, the key is matching the right pump to the right environment. If you would like help choosing which model suits your setup, use the Pump Finder.
