How to Troubleshoot, Fix, and Replace a Float Switch

Sump and sewage pump float switches automatically control the starting and stopping of pumps based on a basin’s water level. These switches can sometimes fail, causing the pump to run continuously and heat up. Also, a broken pump can lead to a flooded basement. It is necessary to troubleshoot these float switches and, if needed, replace them.

Table of contents

• Float switch for sump and sewage pumps
• What causes a float switch to fail?
• How to replace a float switch
• FAQs

Float switch for sump and sewage pumps

A float switch in a sump pit automatically turns a sump pump on and off. The switch moves up and down with the water level of the pit and rises as the water level rises. When the water level rises to a determined amount, the switch turns on and triggers the sump pump to discharge the water from the pit into a dry well or tank. As the water level decreases within the pit, the float switch enters the ‘open’ state, turning off the pump. Read our article on sump pump float switches for more details on the float switch types applicable in sump pits and how to select them for a particular rating.

A sewage pump transports waste material from a sewage basin to a septic tank or a sewer system. A sewage pump float switch moves up or down with the liquid level in a sewage basin. It is an electromechanical switch that turns the basin's sewage pump on or off, depending on the level of the liquid.

What causes a float switch to fail?

If a sump or sewage pump fails, always check the float switch before deciding to replace the pump. A float switch can fail due to multiple reasons.

• Incorrect configuration: Always refer to the float switch manual and the equipment used in conjunction with it (like a sump or sewage pump). The manual contains details regarding the wiring and the various configurations to make the float switch function in the ON and OFF states.
• Poor maintenance: A poorly maintained float switch can fail over time due to the debris that accumulates on its surface.
• Insufficient rating: A float switch has a rating to indicate the electrical load that it can handle. The float switch manual gives the switch’s technical specifications like the cable length, the maximum temperature of operation, and the power rating. Using a load that exceeds the float switch rating can generate heat at the switch contacts, causing it to malfunction.
• Incorrect design: Float switches are made from different materials or specific mechanical configurations based on their application. The wrong switch type may function in the short term, but it is more likely to fail or malfunction.
• Stuck float switch: A float switch stuck in the ‘on’ position may be due to the system clogging or the float switch getting tangled up. The motor may not start or won’t be able to stop at certain times if the float switch gets stuck. This can eventually burn out the motor. If the sump pump has expelled a lot of air or there is water sloshing all around, the float switch may get stuck on the sides of the sump pit.
• Float switch type : Vertical float switches are less likely to become stuck. Tethered float switches have a tendency to become stuck on the sump pit’s side walls, resulting in a flooded basement. Use vertical float switches wherever possible; check the basement area during every major storm if using tethered float switches.
• Debris: Debris in a sump basin can cause the float switch to remain stuck. Ensure to clean the sump basin periodically. Also, the float switch can rust over time and needs replacement.

How to replace a float switch

When a sump or sewage pump doesn’t function according to its rated capacity, it is necessary to detect whether the issue is with the pump or the float. For this, unplug the pump from the switch and plug it in separately. If the pump works well, the float switch is bad. Replace a broken or malfunctioning sump or sewage ejector float switch by performing the following steps:

Retrieve the sump/sewage pump

1. Disconnect the plumbing tubes and remove the pump from the pump basin.
2. Take the pump plug out of the electrical socket.
3. Use a dry towel to clean the dust and dirt off the pump and its wires. Get rid of extra grime by using a powerful hose to spray the pump.

Clean the float switch

1. Degrease and remove extra moisture from the float switch using a dry towel. Dirt and grime accumulated on the float switch can cause it to malfunction.
2. Replace the sump pump. Check if the float switch functions well. If not, it is necessary to swap out the switch.

Disconnect the float switch

1. Pull out and unplug the sump pump. Use a screwdriver to remove the float cap on the pump.
2. Take notes of the wires linked to the float switch inside the sump pump cap. This helps to wire the new float switch with ease.
3. Draw the wires away from the switch and disconnect the float switch cables carefully.

Replace the float switch

1. Unscrew the float switch where it attaches to the cap.
2. Install the new float switch in the same location as the previous one.

Finishing up

1. Clean the wires of any dust or rust. Wire up the new float switch using the wiring diagram noted in Step 3. Read our article on float switch wiring article for the wiring and connection details of float switches.
2. Put the sump pump’s float cap back using a screw.
3. Reinstall the sump pump in the pump basin. Reattach any electrical or plumbing lines that may have been cut off while removing the pump.

Piggyback float switch

Another option is to add a new external float switch with a piggyback plug to bypass the existing switch. This method is easier than replacing the sump pump float switch. A piggyback float switch connects the float switch’s plug to a standard power outlet. A piggyback plug has prongs on one side and an additional outlet on the other. A piggyback connector allows the user to unplug the cords from the wall, separate them, and plug the pump directly into the outlet without the switch, thereby allowing it to test the pump by itself.

1. Run the sump pump continuously to drain all the water from the pit. Then, disconnect the power.
2. Bypass the circuit on the original float switch. Use silicone sealant to seal the housing thoroughly.
3. Attach the replacement float switch to the pump housing with a zip tie. Plug the switch into the outlet and plug the bypass plug into the switch.
4. Fill the pit with water. Adjust the attachment point on the new switch so that the pump turns on at the correct water level.
5. Tighten the zip tie to secure the new float switch.

FAQs

How do you test a sump pump float switch?

Fill the sump pit with water slowly. The float switch should turn on the sump pump to drain the water as the water rises. If this happens, the sump pump float switch is in good condition.

Why is my float switch not working?

Incorrect float switch configuration, poor maintenance, or using a float switch that was not designed for the particular application can cause the float switch to malfunction.

What causes a sump pump float to remain stuck?

The common reasons for a stuck sump pump float switch are blockages and dirt buildup within the basin.

What does a float switch do in a septic tank system?

When the sewage in the septic tank rises to a certain level, the float switch activates the sewage pump to drain out the waste.