If you have two reservoirs then you likely have two solenoids. Its unlikely they would both fail open at the same time, so I would be looking at the switch that controls the solenoid to see if it's stuck closed. I would put a meter on the contacts of the switch and confirm it only has continuity when the switch is depressed. If it always has continuity, then you need a new momentary switch.
I've had mine leak out due to a leak at the hose clamp at the solenoid. The blue crystal residue from the leakage is easy to spot.
