What is a water leak sensor?

Put sensors at the low point beside anything that stores or moves water. The short list: under the water heater, in the washing machine drain pan, at the dishwasher toe kick, under both bathroom vanities and the kitchen sink, behind each toilet, beside the sump pit, at the furnace condensate pump, and under the air handler. Water runs downhill, so the puck belongs flat on the floor, not on top of the appliance where a drip can miss it entirely. A six-pack covers a typical three-bedroom house. Give the first two to the water heater and the washer, which cause more claims than anything else in the building.

The sensor converts a slow disaster into a five-minute cleanup. A weeping water heater fitting can run for days behind a panel; a burst supply line under a sink pushes 5 to 8 gallons a minute, which is well over a thousand gallons across a weekend away. Wet drywall and framing start growing mold in 24 to 72 hours, and by then a mop-up has turned into a $5,000 to $15,000 remediation with a $1,000 to $2,500 deductible attached. The sensors themselves fail quietly. A CR2032 coin cell lasts 1 to 3 years, AA cells 2 to 5, and a dead sensor looks exactly like a working one sitting on the floor.

Test each sensor twice a year by pressing a damp paper towel across the contacts and confirming both the local siren and the phone alert. The test cadence pairs neatly with daylight saving weekends, the same trip as smoke alarm batteries, and the maintenance checklist adds pulling each puck to wipe corrosion off the contacts. Replace batteries on a schedule instead of waiting for the low-battery chirp, and count on 5 to 10 years from the sensor itself. For what an unmonitored leak actually bills out at, see the cost breakdown.