Are water leak sensors worth installing?

There are two kinds, and people mix them up.

Point sensors. Amica describes point or leak sensors as devices that "detect and monitor moisture or humidity where it doesn't belong." In practice that means a small unit that sits on the floor and reacts when water touches it. Most sound an alarm, and some also send a phone alert.

Whole-home monitors. These attach to your main water line or meter and watch flow. Amica describes them as devices that "attach to your main plumbing line or water meter," and describes the all-in-one type as devices that measure flow, pressure and temperature, and can both notify you and stop a leak automatically. Moen says its Flo Shutoff is a device "installed directly on your water line" that detects leaks, alerts you through the Moen Smart Water App, text, email or a phone call, and shuts your water off automatically, and that you can turn your water on and off remotely from your phone.

The big difference is what happens next. A point sensor only warns you, and it can't close a valve. A whole-home monitor can act while you're at work.

For most homes, a few cheap point sensors are worth it. A slow leak can run for weeks behind a cabinet or under a water heater, and by the time you see a stain the subfloor may be wet. A sensor catches it on day one. Put them at the places leaks start:

• The water heater. A tank that fails leaks from the bottom. Water heater leaking from the bottom covers what to do.
• Under kitchen and bathroom sinks. See how to fix a leak under the sink.
• Behind the washing machine and by the dishwasher. Hoses fail here. How often to replace washing machine hoses is worth a read.
• Next to the toilet and near the ice maker line.
• Near an air conditioner drain pan, if yours sits above living space.

In Arizona, where many homes are slab-on-grade, a leak under a slab or in an attic can be hard to notice. A sensor helps with the visible ones. It won't help with a slab leak, which is why signs of a slab leak in Arizona and a look at your meter matter as much as the gadget.

A point sensor only works if someone is home to hear it. If you travel, spend summers away, or run a rental, pick a model that sends a phone alert, and put a friend or neighbor on the notification. A sensor that beeps in an empty house is a smoke detector with no one home.

A whole-home monitor makes sense when the cost of a big leak is high and nobody is around to respond: a second home, a rental, a house you leave for weeks, or a two-story home where a burst upstairs would do a lot of damage. It also catches the leaks a point sensor can't, such as a small drip inside a wall, because it sees the flow.

It costs more than a sensor, and installation depends on the type. Amica says flow monitors are easy-to-install devices, and that you can install some all-in-one devices over your existing plumbing in minutes, while others require a plumber to install them in your main water supply. A unit with its own shutoff valve, like the Moen Flo Shutoff, goes directly on your water line, which means work on the main line, so ask a plumber whether to have it installed. That's the honest trade-off, and for a house you're in every day, point sensors cover most of the risk. Ask a plumber which type suits your home before you buy.

If you already know your water pressure runs high, fix that first. Pressure that's too high is hard on hoses and fittings. What home water pressure should be explains the numbers.

Some insurers do. Amica says that if you own and use leak detection devices, "you may qualify for a discount," and it names three device types: point sensors, flow monitors and all-in-one devices. Amica also notes that discounts aren't available in all states and may vary. It does not say how much.

So don't buy a sensor for the discount without checking first. Call your agent and ask three things: which devices qualify, whether the discount needs a shutoff device or a plain sensor, and whether they want proof of installation. If a discount is offered, it's a bonus, not the reason to buy.

A sensor also doesn't replace maintenance. The Insurance Information Institute says a policy "will not cover damage due to lack of maintenance," so replacing old hoses and supply lines is still on you. Once a sensor goes off, shut off the water at the fixture valve or the main, dry the area, and find the source. If you can't, or the leak is in a wall or under the floor, HQ offers free estimates and upfront pricing, and we're available 24/7 for emergencies.

Have a plan before the alarm sounds, because you'll be half asleep when it does.

1. 1Shut off the water to the fixture. Every sink, toilet, washer and water heater has its own shutoff valve. Turning it off stops the leak in seconds. If you can't find the source, close the main valve at the house. For a split supply hose behind the washer, see what to do when a washing machine hose bursts.
2. 2Look before you mop. Find where the water is coming from. A wet sensor under a sink might be a drip from a supply line, a loose trap, or condensation on a cold pipe.
3. 3Dry the area fast. Move things out of the way and run fans. Wet drywall and cabinet bases are where mold and swelling start.
4. 4Photograph the damage. Take pictures before you clean up, in case you file a claim.
5. 5Reset and retest. Dry the sensor, put it back, and test it again by touching a damp paper towel to it.

Then look at the part that failed. A worn supply line or hose is a simple swap you can often do yourself. A leak inside a wall or under a slab is a job for a plumber.

Keeping sensors working. A sensor that has a dead battery is worse than none, because you think you're covered. Test each one when the clocks change, and replace batteries at the same time. Check that alerts still reach your phone, and that the sensors are still clean and sitting flat. If you move a sensor to clean, put it back in the same spot. Sensors also don't last forever, so when one starts giving false alarms or won't pass the paper towel test, replace it. Two or three inexpensive sensors in the right places beat one fancy unit in the wrong one.