Where leak sensors go

Start where the water comes in

IBHS names washing machines, dishwashers, refrigerators and water heaters as the systems that tap a home's water supply and the points where it fails. Triple-I says to check the hoses to each of them. A sensor does not fix any of these; it tells you the moment one fails, while the water is still a puddle.

One sensor per spot, on the floor

1. Water heater: On the floor beside the tank, under the drain valve and the relief valve's pipe.
2. Washing machine: On the floor behind the machine, where the supply hoses meet the wall valves.
3. Dishwasher: Under the sink beside it, where its supply line and drain hose connect.
4. Refrigerator ice maker: On the floor behind the refrigerator, at the thin supply line.
5. Sink: On the cabinet floor under the sink, below the shutoff valves and the trap.
6. Toilet: On the floor behind the bowl, under the supply line.
7. Sump pit: At the rim of the sump pit, so it reads wet only when the water climbs past where the pump should have caught it.
8. Air conditioner drain pan: In or beside the furnace's condensate pan, or under the condensate pump.

Make them talk to something

A sensor that only beeps helps only when someone is home to hear it. One that reports to a hub can alert your phone, and in Home Assistant a leak sensor is a binary sensor with the moisture device class, so every automation on this site can watch it. The plan builder writes those automations for the sensors you actually have.

Then watch the sensors themselves

Battery sensors die quietly. A sensor that has gone silent looks exactly like a dry floor, so the plans here add one more alert: any sensor that stops reporting for 24 hours. The editor's house uses the same window.