Cloud RO uses Bluetooth to connect to your phone and send alerts. The system collects and stores data until a device running the app is in range. That means you have to be near your Cloud RO system every so often with the mobile app open to receive alerts. I make it a point to open the app every few months when I’m near the system to see the current water quality and filter status information. If you never open the app within range of the system, you’ll never receive alerts.