Shelly's US store listed the Flood S Gen4 as new and in stock for $27.99 on August 26, 2026. The company's European store also showed stock at €18.90, including VAT. The compact Matter sensor is now orderable in both regions.
The S model is built for one leak-prone spot. Three broad stainless-steel pads sit on its base, and Shelly says they can detect clean or low-conductivity water such as air-conditioner condensate. The IP67 enclosure, built-in buzzer and low profile suit the floor below a sink, dishwasher or washing machine. Shelly estimates up to two years from the included CR123A battery, but Matterhome has not tested its sensitivity, battery life or alarm volume.
Matter uses Wi-Fi here, not Thread. Shelly's documentation identifies the exact model as S4SN-0071Z and lists Matter over Wi-Fi alongside Wi-Fi 6, Bluetooth and Zigbee 3.0. A Thread border router is irrelevant, while reliable Wi-Fi at floor level matters. Metal appliances, cabinets and utility rooms can turn an apparently easy placement into a weak-signal location.
The multiprotocol label also needs reading carefully. Shelly's instructions say five quick button presses switch the sensor from its default Matter firmware to Zigbee, or back. Matter and Zigbee are therefore setup choices, not two parallel control paths. Choose the platform first, then pair and test the water state, notification and any shutoff automation before leaving the sensor unattended.
Buy the Flood S Gen4 for a compact spot alarm when Wi-Fi is strong where water would collect. The larger Shelly Flood Gen4 costs $39.99 in the US but uses a two-metre sensing cable, which is the better shape for covering the edge of a water heater, a long cabinet run or several adjacent leak points.
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