This is what we have on our tankers. Rear line goes to the air tank and the other 2 go to the air bag leveler. Push the knob in to dump, pull to inflate. Or just release the brakes and the knob will pop out on its own and bags inflate.
It does not evacuate the air tanks, only the bags.
'15 F150 Ecoboost Maxtow Scab '13 Freedom Exp. 233RBS
Days camped 2016 53,
Days camped 2015 33,
Days camped 2014 47,