I'm looking at piping an indoor wood boiler to my oil boiler and also to my dump zone in either copper or black iron pipe. It looks like ill be going with black iron as it is much cheaper, but I was going to price copper anyway. My question is what type of copper should I be using in the 1" 1.25" sizes, Type M, Type K, Type DMV, etc. Whats there difference and what do you recommend (best value for the money)?