Use a normally closed solenoid just before the dosing pump plugged in to the same outlet as the the pump. That will keep the solution or water from siphoning out of the line. When the pump turns on, the solenoid will open. When it turns off, it will close and the water in the line will remain there. I keep one on my ATO dosing pump for that very reason as well as for a failsafe via my Apex.