You need a drip leg under the stack. You don't want rain water going
directly into your heater.


Ok, does this drip leg need some mechanism for draining the water
out, or is there little enough of it that it's expected to evaporate
by itself?
Looking at the retrofit chimney liner retrofit kits, there doesn't
seem to be any such mechanism, just a cap for the bottom of
the T. And with a rain-cap there shouldn't be very MUCH outside
water.
What code book covers the rules for this sort of thing?
Is it buried somewhere in the building-code, or do I need
to go find the mechanical code-book, too?

--Goedjn