+2. The only other thing I'll add here is this: as you observed, it doesn't have a valve, it's just an open hose that overflow drains the FW tank when it gets too full and allows air into the tank as you use water (so you don't create a vacuum inside the tank and possibly collapse the tank in on itself.) But what I found (both with my previous camper and my current one) is that when I would fill up my FW tank at home and then head out on the "up and down, up and down" interstates around here--by the time I got to where I was camping, I would often have lost a third of the water in the tank out the vent (like, it said "full" when I left home and said "2/3" when I got where I was going.) So I added a valve on the vent/overflow hose as well to keep the water in. You just have to remember to open it when you get where you're going.
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)