Are you curious about how a submersible pump knows exactly when to start or stop? In this in-depth guide, we'll explain the technology behind the float switch and help you make the right choice for your specific situation.
What exactly is a submersible pump with float?
A submersible pump with a float switch is an essential tool for anyone dealing with water management. Whether it's a flooded basement, a swimming pool that needs draining, or an overflowing rain barrel, the float switch acts as the pump's brain. Without one, a pump would have to be turned on and off manually, which is not only impractical but also risky. If a pump continues to run when there's no water, the motor can overheat (run dry).
The float switch operates based on the water level. As the water rises, the float moves upward. At a preset point, the float activates an internal switch that closes the circuit, causing the pump to start. Once the water level has dropped sufficiently, the float drops back down and breaks the connection, stopping the pump.
The different types of float switches explained
Not every situation requires the same technology. Depending on the available space and the type of water (clean or dirty), you can choose from various systems. Understanding these differences is crucial to avoid purchasing a pump that doesn't perform well in practice.
The classic float ball (external float)
The most common variant is the floating ball on a cable. This is a robust system that is very reliable in large spaces. The ball floats on the water and requires a certain amount of "stroke" to rise. Its main advantage is its simplicity; there is little that can go wrong with the mechanism. However, in a narrow well, the cable can become tangled or get caught on the wall. The article "What to do if the float gets stuck due to dirt or silt?" explains how to prevent these types of problems.
The internal float (float arm or tube float)
For narrow spaces, a submersible pump with an internal float is the ideal solution. The float is either housed in a housing on the side of the pump or a vertical float arm that moves up and down along a guide. Because the float doesn't extend beyond the pump, it can never get stuck against a wall or pipe. This makes them perfect for drainage pits. You can read more about the specific mechanisms in "Difference between a float arm and a float ball: Which should you choose?"
Magnetic floats and electronic sensors
The most modern versions use magnetism or electronic sensors. A magnetic float contains a magnet that activates a sensor when it passes a certain point. This system is extremely accurate and less sensitive to contamination than mechanical switches. For situations where every millimeter of water counts, electronic sensors that respond to as little as 1 mm of water are the best choice.
Which float technology suits your situation?
When choosing a submersible pump with a float switch, consider the pump's intended use. If you're using the pump in an open pond, an external float ball is ideal. However, if you're installing the pump in a small basement sump, always choose a model with an internal float switch or a vertical switch.
Adjustability is also important. Some pumps offer the option to adjust the float height, allowing you to determine the water level at which the pump switches on. This is discussed in detail in "Self-regulating pumps: The advantages of an adjustable float height ."
Submersible pump with water sensor 3mm
Safety and installation
A float switch operates with electricity in a wet environment. It is therefore vital that the installation complies with applicable standards. Always ensure a grounded electrical outlet and a properly functioning residual current device (RCD). For safe installation in damp areas, please refer to Safety requirements for connecting a submersible pump to electricity .
When installing the pump in a basement, positioning is crucial. The pump must be placed on a level surface so the float can operate unhindered. For a detailed step-by-step plan, please refer to "Installing a submersible pump in the basement: What should you consider?"
Crab Float Water Sensor 3mm
Common float problems
Although float switches are designed for years of use, malfunctions can occur. The most common complaint is: "My pump keeps running." This often indicates a physically blocked float or a faulty internal switch. In the article "Why won't my submersible pump turn off? Causes and solutions," we delve deeper into diagnosing these problems. Should the float unexpectedly fail, it's good to know that many quality brands allow for the float to be replaced separately. See " Replacing the float in a submersible pump: Can you do it yourself?"
Frequently asked questions about float switches
Can I also operate a submersible pump with a float manually?
Yes, most pumps have a manual mode or a clip to secure the float in the "on" position. Be sure to turn the pump off in time to prevent dry running.
What is the difference between a float and a water sensor?
A float is a mechanical buoyancy aid, while a water sensor (often electronic) reacts to contact with water. Sensors can often detect much lower water levels than mechanical floats.
How big should my pit be for an external float?
For a pump with an external float ball, you usually need a space of at least 40x40 cm or even 50x50 cm to prevent the ball from hitting the wall.
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Difference between a float arm and a float ball: What do you choose?
The Ultimate Guide to the Submersible Float Pump: Everything You Need to Know