Interesting; thanks for posting. It appears he took out the larger diameter drain pipe to install that drain valve. Not sure I'd want to do it the same. I'd prefer a slice valve of some sort, similar to what's under my van currently, but one that works with the larger diameter pipe. I also think that the current system on SMBs is asking for trouble in sub-zero temps: you're storing water outside your van that's gonna freeze and break stuff.
2006 RB50 6.0 Diesel
Flatplate water heater (mounted INSIDE), portable butane stove (no propane)