Near Boiler Black Pipe or Copper Preference?

Al Roethlisberger

As I continue to research my near boiler repipe project for next Spring, one of the interesting observations I've made viewing other projects is the mix between using threaded black steel pipe or sweated copper pipe.

One obvious advantage of sweating copper would seem to be the flexibility it offers without having to thread steel. One disadvantage would likely be cost I imagine, although large diameter black steel isn't cheap either ;p


So, to the pros: Why do some choose copper over black steel? Are there any major gotchas or compromises made by choosing one over the other?


And BTW, the application in my case would be to repipe a standard cast iron boiler, supplying hot water heat in an old gravity conversion.

Thanks,
Al

Brad White

I like iron

for that which connects directly to the boiler. If the goal is to minimize the amount of ferrous metals in the system, compared to the boiler, what is the big deal?

The reason I like iron is that it forms a more massive mounting platform for circulators. It just looks better in my opinion. I am partial to EZ Headers or Earthlee products for convenience. From the circulator on out, sure, copper. If new loop mains, copper then PAP for runouts to old risers works nicely. But near boiler? Eisen.

Jim Erhardt_3

I like iron too for strength and over all professionalism. I also "do it the old fashioned way" with lamp wick and grey pipe dope on the nipples/fittings, which unlike using teflon tape, prevents the previously-assembled joints from moving while building the header. Once past the circs, I go to copper.

ALH_4

Copper

Black iron is substantial, but, in general I like copper for flexibility in piping configuration. You can pipe things more cleanly and in a smaller space. If the piping is braced well with strut, strength shouldnt be an issue. As the piping gets larger, copper makes less sense.

Mike T., Swampeast MO

No "gotchas" that I know of. Some claim the possibility of di-electric corrosion when simply attaching copper to the black iron/steel, but I've been into a few gravity conversions with copper near-boiler piping and after at least 3 decades no sign of corrosion of the iron/steel (the less noble metal). One of the more interesting photos I've ever seen here was where di-electric unions were used and the joint corroded and leaked in just a few years...

Since your near boiler piping will be sized down GREATLY from the gravity pipes (VERY good rule of thumb is 1/2 the supply main size minus one more size) even 4" supply mains use commonly available (and inexpensive) 1 1/2" screwed pipe.

As others said, screwed pipe gives very substantial support for circulators and other devices and the near boiler piping will be virtually or even fully self-supporting (assuming of course that the mains are well-supported).

Since the near-boiler piping generally includes other devices there's usually very little cutting and threading--much will use off-the-shelf nipples.

Yes, copper is more "flexible" but somehow it just looks out of place in an old gravity system.