How often should you test water leak sensors?

Short answer

Test the water leak sensors every 3 to 6 months. A leak sensor is a small puck that sits on the floor where water would show up first and sounds an alarm, or sends an alert to your phone, when its contacts get wet. For battery sensors, replace the batteries once a year, whether the sensor has complained or not. A full test of every sensor in the house takes 5 to 10 minutes and costs $0 to $10 for batteries.

Why it matters

Most water damage isn't a burst pipe. It's a slow drip under a sink, a water heater that starts weeping at the base, or a washing machine hose that sprays behind the machine where nobody looks. The water spreads under the flooring and into the wall for days before anyone notices a stain, and by then the repair means ripping out cabinets or drywall.

A sensor catches the first puddle. But a sensor is only a promise, and you can't tell by looking whether it will keep it. The battery runs down. A smart sensor drops off the wireless network when the router is replaced. The contacts corrode. Each of those failures is silent, which is the whole problem: a dead sensor looks exactly like a working one until the day it matters. Testing is the only way to know.

When to do it more often

The schedule has one firm addition: replace the batteries in battery sensors once a year, on a date you'll remember, rather than waiting for a low battery warning that may never reach you.

Beyond that, test sooner after anything that could have broken the chain between the sensor and you. A new router or a change to the home network can leave smart sensors offline. A power outage can reset a hub. A new phone needs the app set up again, with alerts turned on. After any of those, test one sensor and make sure the alert actually arrives.

What you need

Fresh batteries of the type each sensor takes, for the yearly change
A damp cloth or a wet fingertip, which is all it takes to trigger a sensor

Steps at a glance

Make a list of where every sensor is, so you don't forget one behind the washer or under the water heater.
Touch a wet fingertip or a damp cloth across the sensor's contacts.
Listen for the alarm, and for a smart sensor, wait for the alert on your phone.
Dry the contacts and put the sensor back in the same spot.
Check the app or the sensor's indicator for a low battery warning.
Once a year, replace the batteries in every sensor on the same day.

You're done when every sensor on your list sounded or sent an alert, and every battery is either fresh or less than a year old.

Signs it's overdue

No alarm when the contacts get wet, which is the test failing outright.
A low battery warning on the sensor or in its app.
A sensor showing offline in its app, even though it's sitting right where you left it.

DIY or pro

This is as easy as home maintenance gets. There's nothing to open and nothing to adjust, and a child can do the wet finger test. There's no service to hire for it, and if you have a monitored alarm system with leak sensors, the monitoring company's test procedure replaces this one.

The judgment call is where the sensors live. The places that pay off are under the water heater, behind the washing machine, under the kitchen sink and the dishwasher, under each bathroom sink, next to the toilet, and beside the sump pump if you have one. If the test reveals you only have a sensor in one of those spots, that's worth fixing more than any battery.

FAQ

How do you test a water leak sensor?

Wet your fingertip and touch it across the metal contacts on the bottom of the sensor. It should alarm or send an alert within a few seconds.

How long do water leak sensor batteries last?

Usually well over a year, but a weak battery can fail without warning. Changing them once a year on a fixed date is cheaper than finding out the hard way.

Where should I put water leak sensors?

Under the water heater, behind the washing machine, under sinks and the dishwasher, next to toilets, and by the sump pump. Anywhere water would pool first.

Do smart leak sensors work without wifi?

Most still sound a local alarm, but the phone alert needs the network. Test both the sound and the alert, since the alert is what helps when you're away.