I'm not sure if it is Group A specific, but at the very bottom of the reservoir is a separate unit which feeds the cold start water injector. It's capacity is pretty small, so I decided to open it up to the main unit and install a level sensor at the same time.
Here is the level sensor taken from a water spray bottle used on a Subaru STi...
I started by making a circular hole at the very bottom of the reservoir to suit the sender unit and then cut a square hole (easier to make) between the two sections...
Once done, the unit was flushed out thoroughly to remove any plastic swarf. Don't want to jam a pump or block a spray nozzle! The seperate reservoir is clearly evident in the pic below.
The sealing grommet was then put in place..
... followed by the sensor itself...
A view from the top...
Plan is to utilize the OE cold start water pump which will be triggered via a relay by the Cusco water spray controller. This in turn will be boost pressure activated. I'll write more when I get to that stage.
Gary