It changed during the dream, but the last thing it did was that it was a lever that you pushed down, and it opens a check valve or something, so when the water starts flowing it pushes the laver all the way down. I didn't close it but I'm guessing you'd have to push the lever back up.

But it would be cooler to have a push button somewhere that stops the water flow and allows the lever to rise back with a counterweight and close the main valve again by itself.