[travelin texans]

I still have a hard time understanding why some folks buy a rv then don't use the toilet (some don't use the shower either) as it was designed to be used, save money & buy a pop-up or a tent.
I paid for a rv so I'd have all the conveniences of home & didn't have to go elsewhere to do my business. Curious do they use the facilities at home, go elsewhere or have an outhouse.
I understand it's a sh###y job, probably the worst part of rving, but if careful & pay attention it's not that bad & I guarantee everyone has the same bodily function.

As to the OP, some rvs can have a couple feet of 3" piping after the valves with twist/turns that can hold liquid then while traveling it works to the cap.
Pickup a cap with water hose attachment on it & remove that small cap over the open hose before removing the 3" cap, lot smaller stream to deal with.