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Leak and Freeze

Water freezes at 32°F. Every alert on this site fires at 40°F, while there is still time to act.

Leak and Freeze

Sensor plan builder

Tick what your house has. Get every sensor it needs, where each one goes, whether a shutoff valve is worth it, and the Home Assistant automations to paste.

Tell the builder what your house has, from the water heater to the pipes in the garage, and it lists a leak sensor for every place water can start and a temperature sensor for every space the furnace does not heat. It says whether an automatic shutoff valve is worth adding, and why. Then it writes three Home Assistant automations for exactly those sensors: an alert when one gets wet, an alert when a space drops below 40 degrees, and an alert when a sensor goes quiet for 24 hours. It runs in your browser and sends nothing.

Your house

Runs in your browser. Nothing you pick is sent.

  • 9 leak sensors
  • 1 temperature sensors
  • Yes shutoff valve

Leak sensors 9

  1. Water heater. On the floor beside the tank, under the drain valve and the relief valve's pipe. binary_sensor.water_heater_leak Why
  2. Washing machine. On the floor behind the machine, where the supply hoses meet the wall valves. binary_sensor.washer_leak Why
  3. Dishwasher. Under the sink beside it, where its supply line and drain hose connect. binary_sensor.dishwasher_leak Why
  4. Sink 1. On the cabinet floor under the sink, below the shutoff valves and the trap. binary_sensor.sink_1_leak Why
  5. Sink 2. On the cabinet floor under the sink, below the shutoff valves and the trap. binary_sensor.sink_2_leak Why
  6. Sink 3. On the cabinet floor under the sink, below the shutoff valves and the trap. binary_sensor.sink_3_leak Why
  7. Toilet 1. On the floor behind the bowl, under the supply line. binary_sensor.toilet_1_leak Why
  8. Toilet 2. On the floor behind the bowl, under the supply line. binary_sensor.toilet_2_leak Why
  9. Air conditioner drain pan. In or beside the furnace's condensate pan, or under the condensate pump. binary_sensor.ac_drain_leak Why

Temperature sensors 1

  1. Pipes on an outside wall. Inside the sink cabinet on the outside wall, near the pipes. sensor.exterior_wall_temperature Why

Automatic shutoff valve

  • With 9 leak sensors, one valve on the main answers every one of them.

Automatic shutoff valves

Your Home Assistant automations

Download
- alias: "Leak: a sensor is wet"
  mode: single
  triggers:
    - trigger: state
      entity_id:
        - binary_sensor.water_heater_leak
        - binary_sensor.washer_leak
        - binary_sensor.dishwasher_leak
        - binary_sensor.sink_1_leak
        - binary_sensor.sink_2_leak
        - binary_sensor.sink_3_leak
        - binary_sensor.toilet_1_leak
        - binary_sensor.toilet_2_leak
        - binary_sensor.ac_drain_leak
      to: "on"
  actions:
    - action: valve.close_valve
      target:
        entity_id: valve.main_water
    - action: notify.notify
      data:
        title: "Water detected"
        message: "{{ trigger.to_state.name }} is wet. The main water valve is closing."

- alias: "Freeze: a space is below 40 F"
  mode: single
  triggers:
    - trigger: numeric_state
      entity_id:
        - sensor.exterior_wall_temperature
      below: 40
      for:
        minutes: 15
  actions:
    - action: notify.notify
      data:
        title: "Freeze risk"
        message: "{{ trigger.to_state.name }} is at {{ trigger.to_state.state }} degrees. Open the cabinet doors and let a faucet drip."

- alias: "Watch: a water sensor went quiet"
  mode: queued
  triggers:
    - trigger: state
      entity_id:
        - binary_sensor.water_heater_leak
        - binary_sensor.washer_leak
        - binary_sensor.dishwasher_leak
        - binary_sensor.sink_1_leak
        - binary_sensor.sink_2_leak
        - binary_sensor.sink_3_leak
        - binary_sensor.toilet_1_leak
        - binary_sensor.toilet_2_leak
        - binary_sensor.ac_drain_leak
        - sensor.exterior_wall_temperature
        - valve.main_water
      to: "unavailable"
      for:
        hours: 24
  actions:
    - action: notify.notify
      data:
        title: "A water sensor is offline"
        message: "{{ trigger.to_state.name }} has not reported for 24 hours. Check its battery."

Rename each entity to match your own devices, then paste into automations.yaml. The syntax is Home Assistant's current one; see Home Assistant: Automation triggers.

Sources

  1. IBHS: State of the Risk, Interior Water Damage (white paper, December 2024) Insurance Institute for Business and Home Safety, accessed October 25, 2026
  2. American Red Cross: Preventing and thawing frozen pipes American Red Cross, accessed October 25, 2026
  3. Home Assistant: Binary sensor (the moisture device class) Home Assistant, accessed October 25, 2026
  4. Home Assistant: Automation triggers Home Assistant, accessed October 25, 2026
  5. Home Assistant: Valve (valve.close_valve) Home Assistant, accessed October 25, 2026

Drafted with a language model on October 25, 2026 from the sources listed above, each opened that day. Every threshold and count on the page comes from the site's own code, held by a test. The editor samples pages after they publish; nothing here is an inspection of your house or advice from a licensed plumber or insurer.

Found an error? See Corrections.

Sensor plan builder | Leak and Freeze