Piping a woo boiler and its dump zone- What type of Copper?

[NewBoiler]

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)?

 

[in hot water]

Type L is what most contractors use. Type M is a thinner wall, but these days it seems really too cheap, and prone to pinholes. Maybe something to do with country of origin?

It goes M, L, & K M being the thinnest wall. DWV is a drainage pipe (drain, waste, vent), not commonly used for water or heat piping, I'm not sure the wall thickness. The price per foot pretty much tells the wall thickness.

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