> Copper tubing that has red lettering is called type "M" copper and > is used for a basic residential and light commercial plumbing both liquid > and air. Type "L" has blue lettering. It is used for heavy duty > plumbing and air lines and has a higher pressure rating. Both come in > straight hard 10'-20' lengths or in soft rolIs up to 100'. You can > "sweat" the fitting on, use compression fittings, or flare fittings. > I don't remember for sure but suspect the green is for > refrigeration. It is internally dried and sealed at the factory. Comes > in 50' rolls and perhaps 100'. My .02 worth. >Charles Cron M is low pressure light duty, residential water, buried safely in walls. L is medium duty, residential and light commercial, which is higher pressure rated and rugged enough to be exposed. If I was doing an air system in copper, I think I'd go with schedule K, which is heavy duty. You would likely have to go to a plumbing supply house for it, since it's not what the average weekend warrior will be looking for in Home Despot. Water doesn't worry me, and schedule L might be plenty sturdy and safe for most anything, but I find the damage compressed air can do to be scary. Ron N
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