Very interesting..... I never knew they did that. It appears there is a "Y" fitting on the feed pipe from the tender with a pair of shut-off valves to regulate which water source fed the injector. I find it interesting that this was needed on the flattest piece of narrow gauge railroad the Grande operated. North of Villa Grove there was the climb over Poncha Pass, with water tanks at both Villa Grove and Mears Jct. South of Villa Grove was a billiard table. At one time there was a tank in Moffat, which I'm thinking was replaced by a make-shift stand pipe. A 1949 ETT show water available at Moffat.
But, it was 50 miles between Villa Grove and Alamosa and 37 miles from Moffat to Alamosa.....
The Rotaries were a much simpler arrangement. To change the feed from the Rotary tender to the trailing water car, you had to physically disconnect the tank hose from the tender and connect it to the pipe going back to the water car.