Submersible pump with or without float?
Quick answer: if the pump is permanently installed in a pit, basement, or crawl space, choose a pump with a float switch: it will switch on and off automatically and cannot run dry. If you use the pump occasionally and remain present (emptying a pond, emergency), a pump without a float switch is sufficient. For narrow pits or very low water levels, choose an electronic sensor.
→ Go directly to: recommended pumps with and without float switch
What does a float switch do?
A float switch is a level switch. If the water rises to a certain point, it switches the pump on; once the water has been pumped out, it switches it off again. This means you don't have to monitor the pump and prevents it from running dry. Most submersible pumps are cooled by the water itself; without water, the motor will overheat.
With or without float switch: the difference
| With float switch (automatic) | Without float switch (manual) | |
|---|---|---|
| Ideal for | Fixed installation: pump pit, basement, crawl space, rainwater harvesting tank | Temporary use: pond, swimming pool, construction pit, emergency |
| Dry running | Prevented: pump stops itself | Risk: you have to switch it off yourself |
| Presence | Not necessary | Necessary (or timer switch) |
| Low pumping | Float switch stops at a certain level | Pumps until it draws air |
What types of float switches are there?
1. Mechanical float switch (on the pump)
A float on an arm on the pump operates a switch. Simple, affordable, and reliable in clean to lightly contaminated water. Disadvantage: needs space to move and can get stuck due to dirt or fibers. Example: the HOMA Bully C 140 WA.
2. Cable float switch (electromechanical)
The switch is located in a floating ball attached to a cable. By changing the cable length, you set when the pump turns on. Less susceptible to dirt, but the pit must be wide enough for the ball to rotate freely. Widely used in dirty water and construction pumps.
3. Electronic sensor (electrodes)
Two electrodes measure whether there is water. No moving parts, so ideal for narrow pits and for switching when there are only a few millimeters of water. A separate sensor like the RP CRAB float switch turns any 230V pump into an automatic pump: you plug the pump plug into the sensor's socket.
Do you already have a pump without a float switch? You don't need to buy a new pump: with a separate float switch or level switch, you can make it automatic.
Which float switch should I choose for my situation?
| Situation | Advice |
|---|---|
| Spacious pump pit or basement, clean water | Mechanical float switch on the pump |
| Dirty water or construction pit | Cable float switch (less sensitive to dirt) |
| Narrow pit (< 30 cm) | Electronic sensor |
| Floor as dry as possible | Flat suction pump with sensor (switches at a few mm) |
| Automate existing pump | Separate sensor with socket |
Pump without float switch? Note this
A pump without a float switch will continue to run until you unplug it. Stay nearby and switch it off as soon as the water is gone. Never let a pump with the outlet at the top run dry for long: it is cooled by the water. Pumps with a cooling jacket can handle this better.
Recommended pumps
WITH MECHANICAL FLOAT SWITCH
HOMA Bully C 140 WA
Solid German quality pump for basement and pump pit, plug & play.
€366.95
View pump
WITH SENSOR – FLAT SUCTION
Simer 6 + CRAB float switch
Switches on with just a few mm of water and pumps the floor almost dry.
€339.80
View pump setWITHOUT FLOAT SWITCH
Pentair Simer 6
For temporary use: flat suction down to 2 mm with built-in check valve.
€269.50
View pumpOnly need the float switch? Check out the RP CRAB float switch (€99.50) or all separate float switches.
Frequently asked questions
Do I need a submersible pump with a float switch?
Yes, if the pump is permanently installed in a pit, basement, or crawl space and needs to operate independently. For temporary use where you remain present, a pump without a float switch is sufficient.
Can I add a float switch to an existing submersible pump?
Yes. With a separate level switch with a socket, like the RP CRAB, you can make any 230V submersible pump automatic.
Which float switch fits in a narrow pit?
An electronic sensor. It doesn't require space to move, unlike a mechanical or cable float switch.
What happens if a submersible pump runs dry?
Most submersible pumps are cooled by the water. If the pump runs dry, the motor will overheat and can be damaged.
Unsure which pump is right for you?
Tell us the size of your pit and what kind of water you're pumping. We'll advise you for free on the right pump and float switch.
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