The Flo monitors for water and temperature changes, even in hard-to-reach places, thanks to the included extender cable. It also responds quickly to emergencies, sending smartphone notifications, emails, and texts.
Compatible with: Nothing
The Flo by Moen Smart Water Detector responded consistently both to leaks and to connectivity or power issues, and it did so faster than most of the devices we tested. It’s also cordless, so it’s easy to place without having to worry about an electrical outlet. The Flo’s main unit is droplet-shaped and has sensing probes on the bottom of the device; you can also attach a 4-foot extender probe, so you can sneak it into tight spaces. We like that the Flo also measures temperature and humidity and has an onboard audible alarm (although it isn’t very loud). Unfortunately, it doesn’t integrate with popular smart-home platforms, like Amazon Alexa, Apple HomeKit, and Google Assistant, but it does work with Flo’s water shutoff system—a smart water valve that can turn off your home’s water service if it detects a potentially catastrophic leak
Compatible with: Google Assistant, IFTTT
The D-Link DCH-S161 is a great choice because its loud, 80-decibel (dB) alarm pierces long distances in a home. It also has support for Google Assistant and IFTTT (If This Then That), which allows you to link the sensor to other smart devices, so you can ensure that alerts are noticed. The D-Link is one of the few devices we tested that allows you to silence alarms directly on the device as well as in the app, which is useful. An included 6-foot sensor cable is longer than the one used by the Flo, but we found it doesn’t react as quickly to water and connectivity issues, and it doesn’t have a built-in temperature sensor.
The Proteus Aquo is more customizable than any other water-leak sensor we tested. However, there’s no dedicated app, it needs to be plugged in, and it’s twice the price of our top pick.
Compatible with: Amazon Alexa, IFTTT
The Proteus Aquo Wi-Fi Water Sensor is more customizable than any other standalone device we reviewed. You can program alarm times, schedule power notifications, and integrate it with Amazon Alexa and IFTTT. This device also has the loudest audible alarm (85 dB) of any system we tested, and it is the only one that can integrate up to five sensors simultaneously (including one for a sump pump). But that customization can be complicated, there’s no dedicated smartphone app (you use a Web browser to administer it), the device needs to be plugged into the wall, and it’s twice the price of our top pick.