First Alert L1 Wi-Fi Water Leak and Freeze Detector Review

Damage caused by leaks and freezing can cost you hundreds or thousands of dollars in repair work if left undetected for a long period of time. With a smart detector such as the First Alert L1 Wi-Fi Water Leak and Freeze Detector, you can catch and resolve most leaks before they do serious damage to floors, under-sink areas, and walls. The L1 will let you know when water is detected and when the temperature is cold enough to cause a burst pipe, and it’ll tell you if the humidity level hits a certain threshold. Moreover, you can pair it with a Resideo water shutoff valve (sold separately) to automatically turn off your water supply when a leak occurs. At $69.95, the L1 offers peace of mind and can save you a bundle compared with the cost of repairing water damage, earning it our Editors’ Choice award.

Design and Features: Expandable Detection

The pill-shaped L1 has a matte white and gray finish and measures 3.9 by 2.0 by 1.1 inches (HWD). The top of the device has two siren holes and a status LED, and the bottom holds a pair of water sensors and a removable cover for the battery compartment. The status LED flashes orange to warn you of an issue (a leak and/or temperature or humidity event), turns solid blue when the event has been resolved, and flashes white during a firmware update.

(Credit: First Alert)

The L1 is powered by two AA batteries which are included in the box, along with a screw for mounting the device on a wall and a five-foot sensor cable that plugs into a port on the button edge of the sensor. The entire cable acts as a water sensor and can be extended up to 500 feet by adding five-foot extensions, which sell for $14.99 each. In comparison, the Flo by Moen Smart Water Detector ($49.99) supports up to 18 feet of detection using six-foot sensor cables that go for $19.99 each.

Under the hood is a 2.4GHz Wi-Fi radio, a Bluetooth radio, and a 100dB siren. The L1 will send push and email alerts to your phone when water is detected and when temperature and humidity thresholds are reached, but it does not offer third-party integrations via IFTTT applets, nor does it work with the Amazon Alexa, Apple HomeKit, or Google Home platforms, as is the case with the Flo by Moen.

(Credit: John R. Delaney)

The First Alert L1 can be paired with a Resideo L5 WiFi Water Leak Shutoff Valve to automatically shut off the water in your home when a leak is detected. The L5 valve can be had for around $200 if you shop around, but it must be installed by a professional. That’s a lot more reasonable than Flo by Moen’s Smart Water Shutoff valve ($500), which also requires pro installation.

You can control and monitor the L1 with the First Alert by Resideo mobile app for iOS and Android devices. The device appears on the app’s dashboard screen in a panel that displays the name of the sensor and the time of the last alert. Tap the panel to open a screen that shows the current temperature and humidity readings. Below the readings are buttons you can click for weekly and monthly graphs of temperature and humidity levels. This page also offers a timeline of sensor activity, including the type of event, the time it occurred, and when it was resolved. Tap any active event to mute the siren or to dismiss the alert.

At the bottom of the dashboard screen, there’s a battery meter and a settings button that takes you to a menu where you can enable push and email notifications, set temperature and humidity thresholds, and adjust how often the temperature and humidity readings should be updated (once, twice, or three times daily).

(Credit: First Alert)

Installation and Performance: Low-Stress Leak Detection

To set up the L1, I downloaded the First Alert by Resideo app, created an account and a home, and tapped Add Device on the home screen. I selected the L1 Water Leak and Freeze Detector from the list, chose my home, and gave the device a name. I installed the batteries in the device, held the reset button for five seconds until the LED began blinking blue, and then tapped Next in the app. The app immediately recognized and listed the device, so I tapped it and pressed the reset button once to enter the Wi-Fi configuration screen, where I selected my SSID and entered my password. After 10 seconds, the device was connected to my network and the setup was complete.

The L1 worked perfectly in testing. The built-in sensors triggered an alert when they came in contact with just a trickle of water, and the siren was loud enough to be heard throughout the house. The sensor cable worked as intended, as did the mute siren button. The L1 also sent alerts when my temperature and humidity thresholds were reached, and both readings matched those from a nearby Nest Learning Thermostat.

Verdict: A Small Price for Peace of Mind Against Water Damage

With the First Alert L1 Water Leak and Freeze Detector, you can monitor your home for leaks and low temperatures that can lead to burst pipes. It’ll also let you know when humidity levels reach a point where mold can form. It’s relatively affordable and comes with a five-foot sensor cable you can extend up to 500 feet to cover a larger area. Its mobile app sends email and push alerts when an issue occurs, keeps a record of sensor activity, and tracks temperature and humidity levels over time. For additional protection, it can trigger an optional water shutoff valve to prevent further water damage when leaks occur. With a wider detection range and a less expensive companion water shutoff valve than the Flo by Moen, the First Alert L1 is our new Editors’ Choice winner for smart leak detectors.

About John R. Delaney

Contributing Editor

I’ve been working with computers for ages, starting with a multi-year stint in purchasing for a major IBM reseller in New York City before eventually landing at PCMag (back when it was still in print as PC Magazine). I spent more than 14 years on staff, most recently as the director of operations for PC Labs, before hitting the freelance circuit as a contributing editor. 

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