In article DeL4j.3842$Uy.659@trndny07,
"Ivan Vegvary" wrote:
Okay Craig, what do you mean by "high enough"? Does the valve not have to
be at low point to drain the tank? If I have the valve, say, 2 feet high
would I not end up with 2 feet of water in the tank? I'm not seeing the
picture, please explain.

If the valve is connected at one end to an open drain, and at the other
end to the low point in the tank, by a pipe of any reasonable (smaller
is better, here) size, the air in the tank will push the water out of
the low part of the tank and out of the pipe. When air vents you're
done. That's a slight mis-statement, but pretty close to true. Wait a
few seconds with the valve closed for what's left to puddle, and let it
go again. If it helps you to think of a soda siphon bottle, do that. if
you don't know what one of those is, it won't help you to think about
one (youngster.)

--
Cats, coffee, chocolate...vices to live by