Ok, so I have the rigid installation and framing completed in the basement for a finished living room. Getting ready to start running the copper pipe to connect to our oil boiler (forced hot water) and I am confused on the correct piping to get. (My heating guy is going to install the zone valves and hookup to the boiler, but I am going to run all the lines to save some money..he is going to est the pressure prior to hooking up) I measured the current pipe for the 1st and 2nd floor zone, and it looks like it is 7/8 diameter, which would be called 3/4", correct? Also, I see some 3/4" labeled type L and Type M, and it looks like the type M has a higher PSI rating? Just not sure what to purchase...not sure if I can tell if I currently have L or M? Any hints/tricks?