Water alarms and leak sensors

A water alarm is the cheapest flood protection there is: a floor sensor that sounds, or alerts your phone, at the first drop of water.

Used for: Flooded basement and sewer backup Frozen pipes

Our picks

Best smart sensors
YoLink Water Leak Sensor 4 Starter Kit
Four app-connected leak sensors with a freeze warning
US retailers
$72.99–$89.99at YoLink (YoSmart) · prices may have changedPrice checked 3 Nov 2026, 20:54 UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on YoLink (YoSmart) at the time of purchase will apply to the purchase of this product.
Check price at YoLink (YoSmart) (opens in a new tab)
Best DIY shut-off
YoLink Valve Controller 2 Kit with Bulldog Valve Robot
Shuts off your existing main valve, no pipe cutting
US retailers
$299.95–$339.95at YoLink (YoSmart) · prices may have changedPrice checked 3 Nov 2026, 20:54 UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on YoLink (YoSmart) at the time of purchase will apply to the purchase of this product.
Check price at YoLink (YoSmart) (opens in a new tab)
Best simple alarm
Basement Watchdog Water Alarm BWD-HWA
Loud 110 dB alarm; sensor wire reaches into the sump
US retailers
Check price at Abt (opens in a new tab)

Compare side by side

Water alarms and leak sensors compared. Best in each row is shaded, bold and ticked
Specification	Best simple alarm Basement Watchdog Water Alarm BWD-HWA	Best smart sensors YoLink Water Leak Sensor 4 Starter Kit	Best DIY shut-off YoLink Valve Controller 2 Kit with Bulldog Valve Robot
Price		US retailers$72.99–$89.99	US retailers$299.95–$339.95
Our score	Our score: 7.4 out of 10	Our score: 7.8 out of 10(best in this row)	Our score: 7.6 out of 10
Connection	None (local alarm only)	Long-range radio to a hub	Long-range radio to a hub
Phone alerts	No	Yes	Yes
Shuts off the water	No	No	Yes
Alarm loudness	110 dB	not listed	not listed
Freeze alert	No	Yes	No
Battery	9 V	2 × AAA per sensor	4 × AA, or 9 V DC adapter (included)
Hub needed	No	Yes	Yes
Warranty	5 years(best in this row)	2 years	1 year
Where to buy	US retailers Check price at Abt (opens in a new tab)	US retailers Check price at YoLink (YoSmart) (opens in a new tab)	US retailers Check price at YoLink (YoSmart) (opens in a new tab)

Before you buy

Decide who hears it A local siren helps when you are home; app alerts help when you are away. Ideally have both.
Check outage behaviour Smart sensors need the hub, router and internet. Find out what still alerts during a power cut.
Place them low Put sensors by the sump pit, water heater, washer and floor drain.

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Guides

All guides

How-to

Basement flooded? What to do first

Best-of

The best battery backup sump pumps

How-to

How to keep pipes from freezing in a power outage

Water alarm questions

Do smart leak sensors work in a power cut?

Only partly. A YoLink sensor runs on its own batteries and beeps locally, but its manual says it reaches the internet only through the YoLink hub, so app alerts need the hub, router and internet to have power. A battery backup for the router helps.

Can a leak sensor warn me about freezing too?

Some can. The YoLink Water Leak Sensor 4 beeps four times for a freeze warning at a temperature you set in the app. That helps in a cottage or a cold basement, alongside a thermostat with freeze alerts.

Where should water sensors go?

Wherever water appears first: beside the sump pit, under the water heater and washer, near the floor drain and under sinks. Put them flat on the floor, where the first water collects, and test them after fitting.