To an extent it usually is...... when the air is compressed inside the system, condensation occurs and you get extra water. This must of gone and messed with your solenoid.
This same problem happened to us last year. We would pull the dumb valve and a bunch of slime would come out. I am not sure of any way to correct this but a guess can hurt. Try to eliminate the possibility of the liquid flowing into the solenoid by raising up the solenoid to a higher elevation.