Zooz ZSE42 Water Leak XS Sensor

Quick verdict

A tiny, cheap water leak sensor you can scatter under every water appliance in the house. Detects water and sends an instant Z-Wave alert to Home Assistant. Pair it with the ZAC36 valve actuator and you have automated leak detection and shutoff. Catching a leak early is worth far more than the sensor costs.

Standout: Tiny water leak sensor that fits anywhere pipes run. Pair with a Z-Wave valve actuator for automated shutoff.

Notes last checked May 31, 2026.

Compatibility snapshot

Why it stands out

• tiny form factor fits under water heaters, behind toilets, under sinks, anywhere leaks start
• instant Z-Wave alert when water is detected with no polling delay
• pairs well with the ZAC36 water valve for automated shutoff

Reasons to hesitate

• single coin-cell battery (CR2032 on the 700 series, CR2450 on the 800LR) means modest battery life
• Z-Wave signal can be weak if placed in a basement far from the nearest repeater
• no built-in siren, so you need Home Assistant to trigger an alert

Best for

• under sinks, water heaters, washing machines, and anywhere pipes can leak
• pairing with the Zooz ZAC36 valve actuator for automatic water shutoff on leak detection

Avoid if

• you want a sensor with a larger replaceable battery for multi-year life, since this uses a small coin cell
• you need a standalone alarm that works without a Z-Wave controller

Privacy and local-control notes

Battery-powered Z-Wave sensor. No cloud needed. Leak alerts stay local on your Z-Wave network.

Home Assistant support: supported · integration path: Z-Wave JS.

Buying reality check

Price notes: Cheap enough to put one under every sink and water appliance. Buy a handful.

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