[Tfug] *Way* OT... :>

[euvitudo]

Well, you can, but you would have to 'configure' your hose
in a sideways-S shape.  It all depends on the height of the
water, as well as the height of top of the bend outside the
barrel.

Here's an example (ascii-art):
     hhhhhhhh
/-----h----\ h
|     h    | h
|     h    | h
|     h    | h     hhhhh <----
|wwwwwhwwww| h     h   h
|     h    | h     h   h
|     h    | hhhhhhh   h
\----------/           hhhhhhhh


In this diagram (it looks horribly ugly in ff; copy/paste
into vi or emacs), 'w' is the water level, 'h' is the hose.

You want the part of the hose (the arrow) at the desired
water height..  Thence, if the water level goes above
that, it will drain.  If the water is lower (shown), it will
stop.  I think this is what you were looking for.

The idea is that the hose won't drain when the weight
of the water can't push past the lower loop (i.e., when
the water level is below that lower loop.

So, in the end, you could simply use a common
garden hose for this.

Hope that makes sense.

Phil