How to put leak sensors under sinks and appliances
Put battery water leak sensors on the floor under sinks, behind toilets and the washer, by the water heater and fridge, and near a sump pit. Choose models that alert your phone. If you travel often, add an automatic shutoff valve, which a plumber usually has to install on the main line.
Which water leak sensors to buy
Water damage and freezing are a big share of what insurers pay out on homes. Triple-I's figures for 2019 to 2023 show 1.50 claims per 100 insured homes a year, with an average payout of about $15,400. In 2023 this category made up 22.6% of homeowners losses. A sensor can't stop a leak, but it can cut the hours between a drip starting and you finding it.
| Type | What it does | Best for |
|---|---|---|
| Local beeper | Sounds an alarm where it sits | A spot near where people spend time |
| Wi-Fi or hub sensor | Sends an alert to your phone | Basements, closets, and any time you're out |
| Sensor with temperature alerts | Also warns of cold that could freeze pipes | Cold climates and homes left empty |
| Whole-home monitor and shutoff | Watches water use and closes the main when it spots a leak | Frequent travelers, second homes |
A phone alert only helps if your Wi-Fi and the sensor's batteries are alive. Moen's Flo system, one example of a shutoff, sends alerts by app, text or phone call for leaks, low temperatures and running fixtures.
Where to put water leak sensors
Sensors need to sit where water collects first, usually the lowest point on the floor. Start with the fixtures that hold water under pressure all day.
- Under kitchen and bathroom sinks, at the back of the cabinet
- Behind the washing machine
- Beside the water heater
- Behind the fridge, near the ice-maker line
- Beside the dishwasher, if you can reach the area
- Near the sump pit, in case the pump fails
In a slab-on-grade house, focus on the laundry area and the water heater closet. In a house with a basement, add sensors near the floor drain and under any pipes that run along the walls. In a cold climate, put a temperature-alert sensor in a crawlspace or near pipes on an outside wall.
How to set up leak sensors under sinks and appliances
- Map your water sources
List every sink, toilet, appliance and pipe run. Mark the spots where a failure would do the most damage.
- Choose your sensor type
Pick phone-alert models for anywhere you can't hear a beep. Add temperature alerts in cold climates.
- Set up the app first
Connect the sensors at the kitchen table, then give each a clear name like "Upstairs bath sink".
- Place them on the floor
Follow the maker's instructions so the probes touch the floor at the lowest point.
- Add a second contact
Share alerts with a partner or a trusted neighbor who can reach the main shutoff.
- Learn the main shutoff
An alert only helps if someone can close the valve. Find it and show everyone in the house.
- Ask about a shutoff valve
If you travel, get a quote from a licensed plumber and ask your insurer about discounts.
Water leak sensor cost and insurance discounts
| Item | About what it costs | Notes |
|---|---|---|
| Battery leak sensor | Inexpensive; smart models cost more | Moen values its Smart Leak Detector at $50 |
| Flo by Moen shutoff bundle | $499 on sale, $637 regular | For homes up to 5,000 sq ft; a plumber is required, at extra cost |
| Whole-house shutoff, installed | Varies; can be well over $1,000 | One inspector's rough planning range |
Ask your insurer about a discount before you buy. Triple-I's list of common home discounts names alarms and deadbolts, not leak devices, so don't count on one. Moen says its insurance discount programs require you to agree to share usage data with your insurer. Read those terms first.
Common mistakes with a water leak detector
- Buying beepers for places nobody can hear them, like a crawlspace or a closet under the stairs.
- Forgetting that a sensor detects water on the floor, not a slow drip inside a wall.
- Setting alerts only on one phone. Add someone who'll be home or nearby when you're away.
- Trying to cut into the main water line yourself. Installing a whole-home shutoff is plumber work.
- Ignoring low-battery warnings.
What homeowners say about their water leak detector
One owner watched a sensor stay silent through a real leak, so test each sensor after you install it. As a low-tech backup, owners leave a shallow bin under sink traps so a slow drip is obvious when you open the cabinet. (Reddit)
Before you unpack anything into a sink cabinet, lay a waterproof under-sink mat. A slow drip under a bathroom vanity can go unnoticed for weeks. The mat holds the water and makes the leak obvious. Owners in two threads say to line cabinets to protect them from water damage. (Reddit)
Set the washer and water heater in drain pans and put a sensor inside each pan. Owners suggest this in more than one thread. (Reddit)
Put one at every toilet supply line, not just at the washer and water heater. Owners describe whole floors flooded when a plastic toilet feed line let go during the workday. If you want hands-off protection, pair the sensors with a motorized main shutoff valve. (Hacker News)
Some owners prefer sensors with a loud local siren over hub-and-app models, and one old repairman's advice still circulates: don't run the dishwasher or washer while nobody is home, because inlet valves can stick open. (Hacker News)
Questions about water leak sensors
Where should water leak sensors go?
On the floor at the lowest point near anything that holds or carries water. Start with sinks, toilets, the washer, the water heater, the fridge line and the sump pit.
Will a water sensor lower my home insurance?
Maybe, but don't assume so. Discounts differ by insurer and state, and some programs ask for your usage data, so call your insurer before you buy.
Do I need a plumber for an automatic water shutoff?
For a valve on the main line, usually yes. Moen says a plumber is required for its Flo Shutoff. Battery sensors need no plumbing at all.
What you’ll need
Sources: Insurance Information Institute, flo.moen.com, inspectandtest.net
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.