Leak sensors and automatic water shutoff valves

Leak detection devices come in two kinds. Some sense water where it shouldn't be, and others watch how much water is flowing. Some of either kind can also close a valve and stop the water. From 2019 to 2023, 1.5 percent of homeowners filed an insurance claim for water damage or freezing, and the claims averaged $15,400.

Moisture sensors at one spot

A moisture sensor sits on the floor in a spot prone to leaks and alerts you when it gets wet. Good spots are behind the clothes washer, near the water heater, near an air conditioner and under a sink drain. Most run on batteries, and you can place them yourself. When one goes off, you know exactly where the leak is.

A sensor only catches water at its own spot. High humidity can set off one whose sensitivity can't be adjusted.

Flow monitors on the main line

A flow monitor on the main water line watches the whole house's water use. It alerts you when water flows without stopping or in an unusual pattern. Many also track the temperature and warn of freezing pipes.

A flow monitor can't see a leak that isn't part of the water supply, such as an air conditioner's condensate, a roof leak or a dripping drain pipe. When it alerts, it doesn't say where the leak is. An in-line model usually needs a plumber to install it, while some clamp-on monitors can be fitted by the homeowner.

Automatic shutoff valves

In-line monitors on the main line usually include a shutoff valve. A moisture sensor can also be paired with a shutoff valve on the main, so water found in one room shuts off the whole house. A shutoff stops the water from a burst pipe or a failed washer hose at the main. A device with a shutoff usually costs more than one without.

What to check on a device

• The alert. In a basement, a phone alert may work better than a beeper.
• A shutoff. It helps most in a vacation home nobody lives in full time.
• The pipe size. The shutoff valve has to fit your main line.
• Power. It needs an outlet nearby, and a battery to keep working in an outage.
• Fire sprinklers. The device can't cut off water to a fire sprinkler system.
• Certification. Look for ANSI/CAN/IAPMO Z1349, the standard for these devices.

Keeping it working

Once a year, check that each leak detection or flow monitoring device works, and test it the way its manual describes. A flow monitor also needs recalibrating from time to time to keep its readings accurate. Keep moisture sensors clean and in place. Dust and grime build up on them, and they get moved by accident or by kids and pets.

An annotated example

What to do next

If you already have sensors, list where each one is, check the batteries and test them as the manual describes. If your water utility offers leak alerts, sign up.