That is the ex Uintah 023. Been on the Silverton since the took over. It ran between Chama and Durango and is listed as one of the cars, along with 06217 & 06209, used to supply the Monero Tank. Been a couple of good threads on the site with it in the train going through or being used in special water trains. It sat behind the hardware store rusting away for years before they refurbished it. The 0469 has been in Silverton.
The Grande had a lot of water cars and were used primarily as Earl described. Some appear to be used as Aux locomotive water cars though. I have no idea of the "plumbing". This is one of my all time favorite Grande pictures. Dick Dorman gave it to me years ago. The picture is labeled "Locomotives 220 and 276 near La Jara June 5, 1922" by Otto Perry. Each loco has an extra water tender. Again I don't know about the plumbing.
The W-499 looks like it is being used as an aux water tender in many pictures between Alamosa and Antonito but is actually the dual gauge idler car. W-499 was the tender from Uintah #30 and became the tender for rotary OM in 1962. When the friends incorrectly painted it red, you could see the bitg 30 on the rear of the tender and the w-499 on the side as clear as day under the dark paint. They were almost invisible under the lighter gray.
Picture from Dave Grandt