Wirecutter

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.

Consumer Reports

CR's take: The Flo by Moen system is not only the best professionally installed system we test but also the least expensive. The system consists only of the small shutoff unit that gets spliced into your water line; you can buy optional wireless leak sensors for $50 each, or $130 for three.
We tested the system with the optional detectors and, like the other professionally installed models, it was able to detect both small and large leaks. It receives an Excellent rating for leak detection because it comes with a flow sensor built into the shutoff valve unit, wireless leak sensors, and wire probes that can plug into the sensors and be run under a washer or water heater.
The Flo by Moen shutoff valve is weatherproof for homes in warmer climates where the water line might be located outdoors and above ground, but it lacks a built-in battery backup (you can buy one for $250). In addition to alerts for leaks, the Flo by Moen app can also track your water usage by fixture so that you can see the usage difference between, say, a long shower and your washer’s deep fill cycle. If you opt for the wireless leak detectors, you can also get temperature and humidity readings. Last but not least, the Flo by Moen system works with Amazon Alexa and Google Assistant for voice control, allowing you to ask about your home's water consumption.

CR's take: The Flo by Moen system is not only the best professionally installed system we tested but also the least expensive. The system consists only of the small shutoff unit that gets spliced into your water line; you can buy optional wireless leak sensors for $50 each, or $130 for three.
We tested the system with the optional detectors and, like the other professionally installed models, it was able to detect both small and large leaks. It receives an Excellent rating for leak detection because it comes with a flow sensor built into the shutoff valve unit, wireless leak sensors, and wire probes that can plug into the sensors and be run under a washer or water heater.
The Flo by Moen shutoff valve is weatherproof for homes in warmer climates where the water line might be located outdoors and above ground, but it lacks a built-in battery backup (you can buy one for $250). In addition to alerts for leaks, the Flo by Moen app can also track your water usage by fixture so that you can see the usage difference between, say, a long shower and your washer’s deep fill cycle. If you opt for the wireless leak detectors, you can also get temperature and humidity readings.

CR's take: The Flo by Moen system is not only the best professionally installed system we test but also the least expensive. The system consists only of the small shutoff unit that gets spliced into your water line; you can buy optional wireless leak sensors for $50 each, or $130 for three.We tested the system with the optional detectors and, like the other professionally installed models, it was able to detect both small and large leaks. It receives an Excellent rating for leak detection because it comes with a flow sensor built into the shutoff valve unit, wireless leak sensors, and wire probes that can plug into the sensors and be run under a washer or water heater.The Flo by Moen shutoff valve is weatherproof for homes in warmer climates where the water line might be located outdoors and above ground, but it lacks a built-in battery backup (you can buy one for $250). In addition to alerts for leaks, the Flo by Moen app can also track your water usage by fixture so that you can see the usage difference between, say, a long shower and your washer’s deep fill cycle. If you opt for the wireless leak detectors, you can also get temperature and humidity readings. Last but not least, the Flo by Moen system works with Amazon Alexa and Google Assistant for voice control, allowing you to ask about your home's water consumption.

CR's take: The Flo by Moen system is not only the best professionally installed system we tested but also the least expensive. The system consists only of the small shutoff unit that gets spliced into your water line; you can buy optional wireless leak sensors for $50 each, or $130 for three.We tested the system with the optional detectors and, like the other professionally installed models, it was able to detect both small and large leaks. It receives an Excellent rating for leak detection because it comes with a flow sensor built into the shutoff valve unit, wireless leak sensors, and wire probes that can plug into the sensors and be run under a washer or water heater.The Flo by Moen shutoff valve is weatherproof for homes in warmer climates where the water line might be located outdoors and above ground, but it lacks a built-in battery backup (you can buy one for $250). In addition to alerts for leaks, the Flo by Moen app can also track your water usage by fixture so that you can see the usage difference between, say, a long shower and your washer’s deep fill cycle. If you opt for the wireless leak detectors, you can also get temperature and humidity readings.

Water Leak Detector Comparison