Our pick

This D-Link kit includes a plug-in Wi-Fi hub with an optional sensor cable and can connect to up to 16 battery-powered external sensors. It responds quickly to potential problems with both a loud (94 dB) siren and quick smartphone alerts. Compatible with: Google Assistant, IFTTT

The D-Link DCH-S1621KT Whole Home Smart Wi-Fi Water Leak Sensor Kit combines the best capabilities we have available in leak sensors into one bundle. It includes a plug-in hub (and so can only be placed near an electrical outlet), but it also has a removable 19-inch water sensor cable and a 38-inch extension cord to extend that cable's reach. Additionally, the kit comes with a battery-operated sensor the size of a matchbox, which connects wirelessly to the hub up to 300 feet away. The hub can connect to up to 16 additional sensors, responds quickly when it detects water or loses power, and features a loud (94 dB, according to our measurements) siren. The system supports Google Assistant for announcing activity on smart speakers, as well as the web service and app IFTTT (If This Then That) for activating other smart devices (such as a smart bulb) when it detects a leak. Like any leak sensor, it has a few quirks, but it's still the best choice for monitoring more than one spot in a home.

Runner-up

The Flo monitors water and temperature changes, even in hard-to-reach places, thanks to the included extension cable. It also responds quickly to emergencies and sends smartphone notifications, emails and text messages. Compatible with: N/A

The Flo by Moen Smart Leak Detector responded consistently to both leaks and connectivity or power issues, and did so faster than most devices we tested. It's battery powered, so you can easily set it up without worrying about access to an electrical outlet. The Flo's main unit is teardrop-shaped and has sensor probes on the bottom; you can attach a four foot extension probe and sneak it into tight spaces too. We like that the Flo also measures temperature and humidity and has a built-in audible alarm (although it's not very loud). Unfortunately, this model 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 supply if it detects a potentially catastrophic leak.

Upgrade choice

The Proteus Aquo is more customizable than any other water leak sensor we tested. However, it doesn't have a dedicated app, it needs to be connected, and it's more expensive than our other picks. Compatible with: Amazon Alexa, Google Assistant, IFTTT

The Proteus Aquo Wi-Fi Water Sensor is more customizable than any other standalone leak detection device we reviewed. You can program alarm times, schedule power notifications and integrate with Amazon Alexa, Google Assistant and IFTTT. This device also has a loud audible alarm (85 dB) and the system can integrate up to five sensors simultaneously (including one for a sump pump). But that customization can be complicated, and Proteus doesn't offer a dedicated smartphone app (you use a web browser to perform management tasks). Additionally, the device must be plugged into the wall and is more expensive than our other picks.