How to set up an alert

I wanted Home assistant to alert my phone of the Main water tank has a leak. (Is emptying too fast for longer than 1/2 hr)

Monitor Flow Rate

Need to monitor flow rate.

Go to Settings: Devices and Services then Helpers

Click on + Create Helper

Select Derivative

Choose your tank level as the sensor, then select the time duration.

The Helper will use calculate to give hte derivative of the sensor (turn the absolute level into a flow rate).

Create a card in your dashboard and watch the flow rate for a few days.
You will be able to see what the flow rate normally is.

Create an automatic that says When flow rate is below ‘xxx’ warn me.

For me it was when dam tank derivative is below -0.18 send a notification via mobile_app_wayne with message “Dam tank is flowing fast”