Behind the drivers side back wheel/tire. It's usually a push/pull white valve.
"Next to prayer, fishing is the most personal relationship of man" Herbert Hoover
"American by Birth, Southern by the Grace of God"Lewis Grizzard
2016 GMC Denali 3500Dually--2017 CC 36CKTS
Have 2015 Cedar Creek fifth wheel. Look under slide that refrigerator sits on that is where mine is. Think it is a push/pull valve as I recall. If not there call manufacturer and ask customer Service they had to research but finally got back with me.