Is there such a thing as a rotary water valve with no grooves that you can spin on and off indefinetly?

Question

Where do they sell this?

Answer 1

Yes, they're called Ball valves, and any good hardware store should have them. They're basically just like regular butterfly valves, except that instead of flat plate, it has a ball with a hole in the center.

Twist the handle and the hole in ball lines up with the pipe, water flows. Turn it off and the closed end of the ball lines up, no flow.

EDIT: Of course, nothing will work forever, eventually, everything brakes, but ball valves are extremely durable.

Answer 2

Here is a valve that you attach to a hose. I dropped it and broke the on/off handle. The replacement that I put on doesn't have have the stops that allow it to turn only so far in each direction so it turns on and off and on again indefinately if you keep turning it. I bought it in the lawn and garden department of one of a half dozen stores that sell hoses etc.

http://i33.tinypic.com/qx5hcw.jpg