jwith68
Well-known member
NEVER EVER use type "M" copper for compressed air use! The best is black pipe. Don't use galvanized as pieces could flake off and get lodged into orifices or shoot out of an air nozzle. If you must use copper, use type "K" (refrigeration). If you don't want to spend the money on "K" use "L". "M" is used for drains and is not intended for pressure use. Always isolate vibration with a flexible connector between the compressor and the piping. Use dirt legs and pitch the main run to a drain.
You can disagree all you want. I'm a journeyman Steamfitter with 20 years experience. I've seen first hand the damage using the wrong materials brings. I've had to fix a lot of "but the book said..." disasters. Do what you want, I just gave my professional opinion.
I wasn't going to say anything, but on the subject of wrong materials. In your first post you recommend the wrong material yourself: type "K" is not for refrigeration, ACR copper is for refrigeration. Reference the Copper Handbook, table 3e. Dimensionally it is similar, but it is manufactured cleaner inside, and is nitrogen pressurized and capped for shipment, not shipped open. And I myself have been a HVAC-R engineer for over 20 years, and I have seen first hand the effect of using contaminated copper pipe in a system.

