I have a valve in the water line from the well to my seasonal cottage. It
is about 3' deep and is turned with a very long wrench. Each Spring I turn
it a quarter turn, and each Fall another quarter turn. It rotates all the
way around, so it can be a quarter turn either direction.

I was told that the turn in the fall was to allow the water line to drain.
The turn in the Spring is to run again; if I don't position it properly the
water system doesn't hold pressure very long.

It is getting very stiff and I expect I will have to dig it up in the spring
and replace it. I can't really picture what kind of valve it would be that
allows the pipe to drain in one position, but is open in the other. Anyone
know what it is? Maybe some sort of backflow preventer, but not like any I
have seen.
It is an hour drive to the nearest plumbing supply; I don't really want to
dig it up and take it to the store. I would be nice to have one with me when
I dig it up.

Thanks.