I described how I installed a second tank and BenT
put it on his web pages:

http://hometown.aol.com/realsf/howtopage2.html

Note that I did not connect high pressure.  I run
each tank separately.  That is, I run everything off
of one tank until it is empty and then switch to
the other.  That way, I never run out of propane--
in theory.  In fact, I've screwed up so now write in
my maintenance log when I fill a tank.  ;-)

                        Richard A. Jones
                        Boulder, Colorado