Thanks, Fritz, for the color issue.
Phillip is almost right on the piping.
The coaches are all supplied with chemical toilets. The water feeds are for filling the drinking water tanks mounted to the outside of the restroom walls.
These began to appear in 1967, by 1968 all coaches (including "Alamosa") were fitted with these pipes, only on the depot side as the train faces toward Silverton.
By this time, all 6 Open Gons used by the D&RGW were in service.
There are 4 Closed Vestibule Coaches in the Silverton Train roster. #'s 312, 319, 323, and 327.