Add watergate documentation (#35535)

source/_integrations/watergate.markdown

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+---
+title: Watergate
+description: Instructions on how to integrate Watergate with Home Assistant.
+ha_category:
+  - Sensor
+  - Valve
+  - Water management
+ha_release: '2025.1'
+ha_iot_class: Local Push
+ha_config_flow: true
+ha_codeowners:
+  - '@adam-the-hero'
+ha_domain: watergate
+ha_platforms:
+  - valve
+  - sensor
+---
+
+The **Watergate** integration integrates your Watergate Devices (currently Sonic Wi-Fi) with your Home Assistant.
+With this integration, you are able to:
+
+- Control your valve
+- Monitor live telemetry (water flow, water pressure, water temperature)
+- Monitor water usage
+
+## Prerequisites
+
+- You need to have a Sonic device.
+- The Local API feature must be enabled in the Watergate application.
+
+## Supported devices
+
+The following devices are known to be supported by the integration:
+
+- Watergate Sonic Wi-Fi
+
+## Unsupported devices
+
+The following devices are not supported by the integration:
+
+- Watergate Sonic Pro
+
+## Supported functionality
+
+### Entities
+
+The Watergate integration provides the following entities.
+
+#### Sensors
+
+- **Water meter volume**
+  - **Description**: Water volume used by this device for the entire lifetime of a Sonic device.
+  - **Remarks**: It can be used in the Energy Dashboard.
+
+- **Water flow rate**
+  - **Description**: The current flow rate of water through the device.
+  - **Remarks**: Useful for monitoring real-time water usage.
+
+- **Water pressure**
+  - **Description**: The current water pressure in the system.
+  - **Remarks**: Can be used to detect potential issues in the water supply.
+
+- **Water temperature**
+  - **Description**: The current temperature of the water.
+  - **Remarks**: Useful for monitoring and ensuring safe water temperatures.
+
+#### Valves
+
+- **Water valve state**
+  - **Description**: The current state of the water valve (open/closed).
+  - **Remarks**: It is automatically updated when the valve state is changed.
+
+## Data updates
+
+The Watergate integration fetches data from the Sonic device every 2 minutes.
+Thanks to the webhook option, Sonic will provide live telemetry every second when water is flowing directly to Home Assistant.
+
+## Known limitations
+
+The integration does not provide the ability to set auto shut-off thresholds and does not report any events regarding automatically closed valves.
+
+{% include integrations/config_flow.md %}
+
+{% configuration_basic %}
+IP address:
+    description: "The IP address of your Sonic device."
+{% endconfiguration_basic %}
+
+## Removing the integration
+
+This integration follows standard integration removal procedures. No extra steps are required.
+
+{% include integrations/remove_device_service.md %}
+
+## Examples
+
+### Monitor water usage in the Energy Dashboard
+
+The water meter volume entity can be added to the Energy Dashboard, allowing you to monitor water usage.
+
+### Automation ideas
+
+- Turn off the water when no one is at home.
+- Turn on the water when someone arrives home.
+- Send a notification when the water is too hot.
+- Send a notification when the water is too cold.
+- Send a notification when water is flowing for too long.