On Sun, 14 Nov 2010 12:11:02 -0500, "Wild_Bill"
wrote:

A properly installed water heater won't explode.. that's what the safety
relief valve is designed and intended to prevent.

Your propane tank was certified for compressed gas (although liquid and gas)
for use at pressures that are most likely at least 200% more than normal
working pressure.
The actual burst test pressure of the propane tank is much higher than the
working pressure.

Where is the tank drain, or is the tank inverted? Just curious.
Been done both ways. I brazed a heavy washer on the bottom of my tank
and drilled and tapped it for 1/8NPT for the drain.
A friend did it the other way - bottom feed, with the air drawn out 6"
up, and the drain at the bottom (specially made fitting to screw in in
place of the Propane valve)