plumbing old radiators

BigE_nd

Just some general plumbing questions.  I'm looking at replacing some cast iron radiators and plumbing that froze last winter.  It appears that the pipes are black iron, so was planning to use black elbows and fittings from the hardware store and a new brass valve.  Are there any issues with using this material?  Also are there any suggestions for using pipe sealant for this application?   Thanks.

Alan (California Radiant) Forbes

Piping

Black steel pipe is OK to use with your favorite pipe dope.  Try to use black, cast iron fittings instead of the black malleable fittings that are normally used for natural gas.  It's the custom to use cast iron fittings and you can crack them with a sledge hammer if you ever need to modify the piping.

Albany Chris

PEX and black pipe

I renovate old houses, including many freeze ups. Just a thought, I like to use black pipe to come off the radiators and down through the floor, and then in the basement I like to use pex connect them to a manifold right near the boiler. 1/2" pex lines work for all but the biggest radiators since they only serve one each and have minimal fittings. My heating supply guy actually suggested 3/8 for most of the smaller radiators, but I like to keep it simple. Use the valves on the radiators to balance if necessary.

Albany Chris

sealant

Missed your sealant question. When joining new pipe to new, a good pipe dope or a premium teflon tape should work fine. I sometimes have problems connecting to the old pipes so I like to use both and make sure I get on it pretty good when tightening. Sucks having to take apart 10 fittings to get to the one that is dripping.