Sump pump high-water alarm sounding: causes and checks

Short answer: The water in the sump pit has risen to the alarm's float or sensor, so the pump is not keeping up. Common causes are a tripped breaker or GFCI, a float switch stuck against the pit wall or pump, a frozen or clogged discharge line, a failed check valve, or a worn-out pump. Check power and the float first.

Safety: Water and electricity: unplug the pump before reaching into the pit, and never stand in water to reach an outlet. Call a plumber or electrician if the outlet is under water.

Step by step

1. Check power. Make sure the pump is plugged in and the outlet, GFCI and breaker are on. Do this with dry hands and dry footing.
2. Look at the float. A float that is tangled in its cord, snagged on the pit wall or blocked by debris will not start the pump.
3. Check the discharge. Outdoor discharge lines can freeze or clog; if the pump runs but water does not leave, the line or check valve may be the problem.
4. Listen to the pump. A pump that hums but does not move water may be jammed or failed.
5. Test the alarm later. Once the pit is down, test the alarm per its manual so it is ready next time.

Sump alarms and float switches

• "The Original" Sump Alarm High Water Alarm — $184.11
• Level Sense Sump Pump Failure Alarm with 15 Foot Float, High Water Alarm for Sump Pump Sounds a Piercing 120 dB Siren - Self-Charging LiPo Battery Pow — $129.99
• SA-120V-1L-WIFI Alarm minus float — $194.90
• 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
• "SinkWire" Float Switch Connection Kit: Stop Premature Float Switch Failure — 1 — $12.41

Common questions

Why does my sump alarm go off and then stop?

A heavy inflow can lift water to the alarm level briefly before the pump catches up, or the float may be hanging up intermittently.

Do I need a separate alarm float?

A high-water alarm uses its own float or sensor set above the pump's turn-on level so it warns you when the pump fails.

Can a sump alarm text me?

Wi-Fi alarms can send phone alerts; standard alarms sound locally only.

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