433MHz sensor that detects water flooding and sends an RF signal to the automatic WiFi Valve Closer ATTENTION - Communicates only with WiFi eWeLink Valve Closer. It does not communicate with the Sonoff RF Bridge, etc. If the metal contacts of the sensor are flooded with water, they will be electrically connected and the base of the sensor will send a unique RF code. This code captures WiFi Valve Closeer and closes. The user must reopen the valve himself, either manually or remotely via the eWeLink application.