Can't a simple ball valve be installed in-line for each slide?
John Guest makes fittings that can literally be snapped on almost any type of tubing, including metal.
Cut the tubing and put the valve(s) in-line.
Parker-Hannifin dealers sell EVERYTHING that you may need to do this.
Me, Julie, Lil' Barry, Faith, and OSDs, Fang and Treaty
2003 Hyundai Starex (H1), 2012 Coachmen Clipper 126
I don't know when we'll be able to go camping again...