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Float switches are simple but can fail due to a few common causes:
Debris or Grease Buildup: In wastewater, it’s very common for trash, rags, or grease to accumulate on the float. A float switch can get jammed or stuck in the “down” or “up” position because debris is preventing it from moving
If the float is stuck down, the pump won’t turn on; if stuck up, the pump might run continuously. Sludge can also weigh down a float so it becomes less buoyant. Solution: Inspect and clean the float – remove any obstructions or caked-on material so it moves freely.
Tangled or Improperly Mounted: The float or its cable might be snagging. If the float’s tether cord wraps around the pump or another object, it can’t rise properly (“hung up” float). Similarly, if multiple float cables are not secured, they can twist around each other. Solution: Adjust the installation – secure cables separately, use a float tree or spacing device, and ensure correct tether length. This prevents the float from wedging against the tank wall or other floats.
Wiring or Electrical Faults: A float switch can also fail electrically. Loose or corroded wiring connections will prevent the signal from reaching the pump. Or the float’s internal switch contacts can wear out over time (especially with high current loads), causing it to not close the circuit. In some cases, the float cable jacket gets damaged and water intrudes, ruining the switch. Solution: Check the float’s wiring – ensure all connections are tight and not corroded. Test the float’s continuity with a multimeter (should be closed when lifted, open when lowered, for a pump-down float). If the float has failed internally, it will need replacement.
Float Waterlogged or Density Change: Occasionally, a plastic float can develop a crack and fill with water, losing buoyancy. Or if the liquid’s specific gravity is unusual, the float may not float as designed. In these cases the float might sink or not rise enough. Solution: Replace any float that has water inside it (you’ll notice it sloshing or it feels heavy). For unusual liquids, consult the float manufacturer for compatibility (you might need a special float designed for oil, foam, or high-temperature liquids).
Troubleshooting tip: Most often, float problems in sewage systems come down to debris and corrosion issues. Regular inspection and cleaning can dramatically reduce these failure incidents.