Howdy, Allan…
There is no concept of “Primary Control”.
A Tile in ActionTiles is tied to a specific Capability. A Thing with many Capabilities can generate Tile Types for each such Capability.
In this particular case, our Valve Tile currently has a hardcoded Fountain Icon available, but our Switch Tile does not. @JB_Bentz is using a Switch to control his fountain valve.
Thus, a functional DTH hack would be to create a copy of the DTH for the Switch, and add capability "Valve". He would also have to add the open()/close() Command methods, and have those internally mapped to call “on()/off()”. He could then generate the desired functional Valve Tile.
There are other options such as using a Virtual Valve and universal device translator or other basic synchronizing SmartApp.
But frankly, except for the joy of hacking, these solutions are excessive (using a screwdriver to pound in a nail) - considering that ActionTiles will almost certainly be making icon usage more flexible in the coming months.