Welcome to the forum! On my camper the valve for the inside kitchen gray tank is inside the left rear tire. The valve for the shower and outside kitchen gray tank is behind the left rear tire. The kitchen valve isn't easy to reach.
2013 Silverado 2500HD LTZ CC 6.6L Duramax Diesel
2014 Sunset Trail SF270BH
Holly & Buster, mini Dachshunds
2016: 1 trip, 3 nights in 1 state, 316 miles
2015: 5 trips, 18 nights in 3 states, 2707 miles
2014: 5 trips, 14 nights in 3 states, 2426 miles