Automatic shutoff valve on the main
Moen Flo Smart Water Monitor and Automatic Shutoff Valve, 3/4 in
A motorised valve installed on the main cold-water line that measures flow, pressure and temperature, runs a daily micro-leak test, learns the household's usage, and closes itself when it sees a leak — the only product here that stops the water.
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Best for
Whole-house protection — a second home, a finished basement, or any house where a leak would run for hours before someone noticed
Specifications
| Pipe | 3/4 in main (900-001); 1 in and 1-1/4 in models sold separately |
|---|---|
| Measures | Flow, pressure and temperature; daily automatic MicroLeak tests |
| Sensitivity | Leaks as small as a drop per minute (Moen) |
| Shutoff | Automatic on a detected leak; remote and manual shutoff from the app |
| Learning | FloSense learns the home's usage pattern to flag abnormal flow |
| Alerts | App, phone call, text and email (Moen Smart Water app) |
| Power | AC outlet (100–240 V) with continuous power near the valve; 12 V DC adapter with 10 ft cable included; 25 ft extension sold separately |
| Wi-Fi | 802.11 b/g/n, 2.4 GHz |
| Pressure / temperature | Max operating pressure 175 psi; ambient 32–140 °F |
| Install | On the accessible main cold supply after the meter, shutoff and pressure-regulating valve; Moen recommends a licensed plumber |
| Certifications | IAPMO IGC 349; UL 1951, CSA C22.2 No. 14 and 68; NSF 61/9 and NSF 372; FCC Part 15 |
| Works with | Amazon Alexa, Google Assistant, Alarm.com, Ring |
| Warranty | 1 year; FloProtect subscription extends to 5 years and adds up to $5,000 deductible coverage |
| In the box | Valve, two 3/4 in NPT brass tailpieces, AC adapter, spare o-rings, installation spacer, hex key |
Specifications as published by Moen. Confirm against the current spec sheet before buying — manufacturers revise models without renaming them.
What's good
- Closes the main automatically — a burst washer hose at 2 a.m. becomes a puddle, not a flooded floor
- Catches the leaks sensors never see: a pinhole in a slab line or a running toilet shows up in the daily pressure test
- Flow, pressure and temperature on the app, with a freeze warning when the line gets cold
- Certified to NSF 61/372 for drinking-water contact and listed to UL 1951
What's not
- A plumbing job on the main: Moen recommends a licensed plumber, and the valve needs a nearby powered outlet
- Standard warranty is one year; the 5-year coverage is tied to the FloProtect subscription
- Only watches water that passes through it — a leaking water-heater tank or a sump failure still needs a floor sensor (Moen sells its own Flo Smart Water Detector)
- Needs 2.4 GHz Wi-Fi and continuous power; it keeps its position on a power cut but can't alert
Our verdict
The only answer to 'what if nobody is home'. Sensors raise the alarm; this closes the valve. Budget for the plumber, put an outlet within reach of the main, and keep a floor sensor at the water heater for the one failure a valve on the main can't see. For a house that sits empty for weeks, it is the piece that earns its cost.
Frequently asked questions
Compare with the alternatives
- Govee GoveeLife Water Leak Detector 1s (H5044 gateway + H5059 sensors) — a first leak-alarm kit for the water heater, washing machine and under-sink spots in a house with 2.4 ghz wi-fi
- YoLink Water Leak Sensor 1 Starter Kit — Hub + 4 Sensors (YS1603 + 4 × YS7903) — big or multi-level homes, basements and outbuildings where range and battery life matter more than a built-in siren