On Jan 22, 8:18*pm, David Nebenzahl wrote:
On 1/22/2011 3:38 PM Bob F spake thus:

My understanding is that sulphur or something in some gas can cause problems
with galvanized piping, so if the local supply has it, galvanized may not be
allowed. Part of the problem may relate to the zinc flaking off the iron, and
plugging orifaces. The drop tube below the "T" to the burner is there to catch
such debris, I believe.

Y'know, this business of how gas might *possibly* cause the coating to
"flake off" of galvanized piping has been brought up several times in
this thread. But nobody has provided any evidence for this, not even
anecdotal. Certainly no articles in scientific journals or the like.

I've been looking for more information as well, and I have to agree
with you. There's a lot of conjecture and a lot of argument about
it. Like I've said, this topic starts wars. Maybe it's like a
plumbing WMD - wars with no foundation!

So until I see such evidence, I'm going to write this off as basically
urban legend, from the dim, dark past of gas companies who didn't really
know *what* was happening.

But I still use black pipe only on gas, just from force of habit ...

I recently replaced part of the 1.5" black iron condensate return line
on our one-pipe steam system. The pipe was original to the house and
about 80 years old. A few years back we had a leak on, you guessed
it, the night before Christmas Eve. It had rusted through at the
first vertical to horizontal transition on its return run. The
outside of the pipe was quite rusted in places, and, because of that
leak, I figured the pipe was just about done and I wasn't going to
wait for another leak. When I busted off the first fitting and
removed that first section of pipe, I was quite surprised to see the
condition of the inside of the pipe. It looked almost new. There was
a thin, uniform black layer coating the inside, and other than that
was remarkably clean. There was no rust in the pipe or the fittings.
The fitting that leaked was buried inside a wall just about the
basement slab and had rusted from the outside in. The old concrete
foundation wall had been compromised by water intrustion over the
years and what was essentially sand had buried the pipe and kept the
outside of the pipe wet enough to rust at an accelerated rate, but
there wasn't enough water coming through the foundation to show up
inside the living space.

I discovered some new-found respect for black iron pipe from that
abbreviated replace-it-all project attempt - there was no need. In
the same or less time, galvanized pipe of the same size has had to be
replaced at several places in the house. This is backwards to what
everybody 'knows' -galvanized pipe will last longer than black iron -
but I've seen it firsthand. I still don't tell people to go against
code and buy the cheaper black iron pipe if code calls for
galvanized. When I replaced the section of pipe I had cut out, I
replaced it with black iron. I'll let you know in 80 years how it's
held up.

The codes around here are messed up. Until very recently there was
one nearby village that required 3/4" plywood sheathing on the walls
and roof, cast iron subsurface rainwater drainage lines, BX electrical
cable (say what?!), two layers of 1/2" drywall laid at right angles
with both layers taped, and slate roofs. Only when the prices of
things got so ridiculous, and the homeowner's started listening to the
contractors telling them that the code did not benefit them in any way
and only wasted large amounts of money, did the village start
modifying their code.

But who tells a gas company what to do?

R