Fix a freeze alarm that sounds
We'll confirm the temperature, warm the area, then silence the alarm—or tell you when to call a pro.
What you'll need
- Thermometer (to check temperature at sensor)
- Space heater or heat tape (if needed)
- Fresh batteries (if the alarm will not reset)
Step-by-step diagnostic
Quick triage — pick your path
Quick triage — pick your path
Choose the option that matches what you see. You can jump straight to that section.
- Follow this guide Work through the full procedure from confirming the temperature to silencing.
- Warm the area You know the area is cold and need to add heat.
- Silence the alarm The area is warm and you need to reset the alarm.
- When to call a pro Pipes have frozen or burst, or you cannot warm the area.
Show full guide
Steps
Goal: Confirm the temperature, warm the area, then silence the alarm.
- Locate the freeze alarm and confirm it is sounding. Check the temperature at the sensor.
- Good: Temperature is below 45°F—warm the area. Proceed to Warm the area.
- Bad: Temperature is above 45°F—sensor or battery fault. Replace batteries or the unit.
Warm the area
Goal: Raise the temperature above 45°F to prevent freezing and allow the alarm to reset.
- Open cabinet doors under sinks. Run a space heater in the area if safe.
- Add heat tape to exposed pipes. See fix-pipe-insulation-is-missing.
- If the furnace failed, see fix-thermostat-will-not-respond. Confirm the temperature rises.
Silence the alarm
Goal: Silence and reset the alarm after the area has warmed.
- Press the silence or reset button. Replace batteries if the alarm will not silence.
- Confirm the alarm stays silent when the temperature is above 45°F.
When to get help
- Shut off the main water supply if a pipe has burst. Call a plumber.
- Call an HVAC pro if the furnace has failed and you cannot restore heat.
Verification
- The temperature at the sensor is above 45°F.
- The alarm has silenced and stays silent.
- No pipes have frozen or burst.
Escalation ladder
Work from the device outward. Stop when the problem is fixed.
- Confirm temperature Check the temperature at the sensor; freeze alarms trigger below 40–45°F.
- Warm area Add heat, open cabinet doors, run faucets, or add heat tape.
- Silence alarm Press silence button after warming; replace batteries if needed.
- Check heat tape or furnace Confirm heat tape or furnace is working if the area is normally cold.
- Call a pro Pipes frozen or burst, or cannot warm the area.
What to capture if you need help
Before calling support or posting for help, have these ready. It speeds everything up.
- Location of the alarm
- Temperature at the sensor
- Steps already tried
Is the temperature at the sensor below 45°F?
Freeze alarms trigger when the temperature drops. Check with a thermometer.
Place a thermometer near the freeze alarm sensor. Good: temperature is below 45°F—warm the area. Bad: temperature is above 45°F—sensor may be faulty or battery low.
You can change your answer later.
Have you warmed the area?
Add heat: open cabinet doors, run a space heater, add heat tape, or fix the furnace.
Open cabinet doors, run a space heater (if safe), or add heat tape. See fix-pipe-insulation-is-missing. Good: temperature is above 45°F. Bad: area still cold—check furnace or heat tape.
You can change your answer later.
Keep warming
Add more heat. Check the furnace, heat tape, and circuit breaker. If pipes have frozen or burst, shut off the main and call a plumber.
Silence the alarm
Press the silence or reset button. Replace batteries if the alarm will not silence. Confirm it stays silent when the area is warm.
Sensor or battery fault
If the area is warm and the alarm still sounds, replace the batteries. If it still will not reset, replace the alarm. Confirm the new unit stays silent when the temperature is above 45°F.
Reviewed by Blackbox Atlas
Frequently asked questions
- Why would a freeze alarm sound?
- Freeze alarms detect cold temperatures that put pipes at risk. Common causes: power outage, furnace failure, open windows or vents in cold areas, or pipes in unheated spaces. Warm the area first.
- At what temperature do freeze alarms trigger?
- Most freeze alarms trigger around 40–45°F (4–7°C), before pipes freeze. Check the alarm manual for your model. The alarm gives you time to act before a freeze.
- When should I call a plumber for a freeze alarm?
- Call a plumber if pipes have frozen or burst, you see water leaking, or you cannot warm the area. Shut off the main water supply if a pipe has burst.
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