Sump and septic float switches: piggyback, tethered and heavy-duty

Short answer: A tethered float switch hangs on its cord and tips up as water rises, closing a switch inside. A piggyback float has a plug-through cord: the pump plugs into the float's plug, so the float switches the pump directly. The free tether length sets the range between turn-on and turn-off. For septic, sewage or effluent tanks, use a float rated for that service.

Safety: Unplug the pump and alarm before working in a pit. Do not enter septic tanks. Hardwired controls should be serviced by a qualified electrician.

Step by step

1. Identify the job. Pump control (turns the pump on and off) or alarm signal (feeds an alarm panel). Use the float made for that job.
2. Check the rating. Match the float's voltage and amperage rating to the pump; for sewage or effluent use a float listed for it.
3. Set the tether. A longer free tether gives a wider range between on and off; a shorter one cycles the pump more often. Follow the maker's chart.
4. Give it room. Mount so the float swings freely without touching the pit wall, pump or other cords.
5. Protect the splice. Where cords are spliced in a pit or tank, use a sealed, wet-location connection method.

Float switches

• 3100 Series Piggyback Sump Pump Float Switch — 10 Foot / Starts Pump on High Level — $42.13
• Float Switch for Sump Pump - Water Level Sensor with Honeywell Microswitch and Adjustable Tether Length for Ground Water Bilge Pump and Water Tank – N — 10 Foot — $32.22
• Float Switch for Sump Pump - Water Level Sensor with Honeywell Microswitch and Adjustable Tether Length for Ground Water Bilge Pump and Water Tank – N — 100 Foot — $157.70
• "Sludge Boss Piggyback" Heavy Duty Float Switch for Suspended Solids (3120 Series) — 20 Foot — $120.28
• "Sludge Boss" Heavy Duty Float Switch for Septic and Sewage — 100 Foot — $258.96
• "SinkWire" Float Switch Connection Kit: Stop Premature Float Switch Failure — 1 — $12.41

Common questions

What is a piggyback float switch?

A float with a plug that the pump plugs into, so the float turns the pump on and off without a separate control panel.

Why does my sump pump turn on and off too often?

A short tether, a float set too low, or a small pit can cause short cycling. A failed check valve can also let water run back in.

Can I use a sump float in a septic tank?

Use a float listed for sewage or effluent service in septic and sewage tanks.

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Related categories: Sump & Effluent Pumps & Alarms · Septic & Wastewater Parts. General information only; follow the equipment maker's instructions and local codes. Updated 2026-11-14.