Difference between a float arm and a float ball: What do you choose?

Are you planning to buy a new submersible pump, but unsure about the type of switch? The difference between a float arm and a float ball not only determines ease of use, but also whether the pump is suitable for your specific situation.

The classic float ball: Reliable but space-consuming

The float ball, also called the cable float, is the most common variant of a submersible pump with a float . The principle is simple: an air-filled ball floats on the water surface. As the water level rises, the ball rises until an internal switch activates the pump. As the water level drops, the ball sinks again, and the pump shuts off.

While this system is extremely robust, it has one major drawback: freedom of movement. A floating ball needs a certain radius to float freely. In a wide well or an open pond, this isn't a problem, but in a narrow shaft, the ball can get stuck against the wall. You can read more about this in " What to do if the float gets stuck due to dirt or silt? "

The float arm: The solution for tight spaces

A float arm (often called a vertical float or internal float) works differently. Instead of hanging from a flexible cable, the float moves linearly along a fixed axle or arm. This makes the submersible float pump much more compact.

Because the float moves only vertically, there's no risk of the switch getting caught on anything. This makes this type of pump ideal for narrow drainage pits or basement shafts where every centimeter counts. For successful installation, we recommend consulting the article " Installing a submersible pump in the basement: What to consider? "

Submersible pump with water sensor 3mm

269,00

The major advantage of the float arm is its precision. You can often set the water level at which the pump should start more precisely. This is essential in situations where flooding must be addressed immediately before it reaches a critical level.

Which float do you choose for your situation?

The choice between a float arm and a float ball depends entirely on the available space and the water's contamination. Here are the key considerations:

Space: If your well is narrower than 40x40 cm, always choose a float arm or a model with an internal sensor.
Contamination: In very dirty water with many solid particles (such as leaves or twigs), a float ball is sometimes less susceptible to failure, because an arm can block more quickly due to caked-on dirt.
Automation: Do you want the pump to switch on even at very low water levels? A float arm often offers more adjustment options.

However, problems sometimes arise, regardless of your choice. In the article " Why Won't My Submersible Pump Shut Off? Causes and Solutions, " we delve deeper into troubleshooting such problems.

Crab Float Water Sensor 3mm

99,50

Maintaining your float system

Regardless of whether you choose a ball or an arm, maintenance is crucial for a long lifespan. Limescale and mud are the biggest enemies of moving parts. A float arm that becomes clogged with limescale will no longer rise smoothly, causing your basement to flood. We explain how to prevent this in " How do you clean the float of a submersible pump? "

Should your system fail after years of faithful service, repair is often possible. In that case, read " Replacing the float in a submersible pump: Can you do it yourself? " to determine whether you can carry out the repair yourself or whether you need to call in an expert.

Frequently asked questions about floats

Can I attach a float ball to use the pump manually?

Yes, many pumps have a clip on the housing to hold the cable. Be aware that this will prevent the pump from stopping automatically and may cause it to run dry.

Why do professionals often choose a float arm in basements?

Professionals choose a float arm for its reliability in small spaces. This eliminates the risk of the pump not starting because the float is resting against a wall.

Is a float arm more susceptible to failure?

Not necessarily, but it does require a quick inspection for dirt buildup around the guide more often, whereas a float ball will often flush clean on its own due to its free movement.