Black Pipe for Hydronics?

Should I be using black pipe to replace the supply and return manifolds connected to my cast-iron boiler. Or galvanized? Currently the setup has black pipe. I'm planning on using brass fittings between the copper and iron.

Also, about how much torque should be applied to tighten the fittings for 1.25" black pipe?

I'm not a pro, but I think you need dielectric junctions between the iron and copper, brass nowithstanding.

Brass alone is fine. You can really torque black pipe without doing any damage. I do not know what the suggested torque is, but I go pretty heavy and I have never run into a problem. I do not know how else to describe torque.

Black Pipe is just fine.
Water in a hot water boiler looses it's aggressiveness (becoming ph neutral) after it has been reheated over and over. Therefore black pipe is fine. Live sprinkler head systems are based on this same principle. No new water = ph neutral water provided nothing new is added or subtracted.