Type K, M or L copper for air lines?

[Blk88GT]

I never paid much attention to this when I did the lines in my old shop, but was wondering what I should be using in my new place.

I'll have a half dozen drops, done in 1/2" copper. Compressor does 125psi, maybe someday I'll go to 175.

Thanks in advance.

 

[KenC]

Search for 'copper tube handbook'. Official pub from the copper industry. Lots of good info, pressure ratings, temp rating etc.

IMO, stay away from M, either L or K will be fine. The joints are the weakest point and the best solution is a silver bearing solder but I've used lead free with no problems. The compressor to building pipe connection should be flexible to both isolate vibration and heat. I used a hydraulic line.

 

[pattenp]

Here you go...

http://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf

 

[Blk88GT]

After looking at the document pattenp linked (thank you!) I don't see why I wouldn't use type M.

 

[CNGsaves]

Discussed many times in recent GJ threads. Good luck in your build.

Use Advanced Search for:

. . . . copper airlines

 

[KenC]

I should have been more clear in my preference not to use M. It is rigid. All changes of direction or plane must be made with fittings. The others can be bent without kinking. So minor offsets can be made by bending. Even 90deg bends, like dropping down a wall after traversing a ceiling, can be done without fittings.

So even though the thicker L/K cost more, if several fittings are needed using M, the overall cost will be less. And, the time is much reduced. As well as your frustration, if you like sweating fittings as much as I do. I wouldn't even consider mechanical fittings, (flare or compression).

 

[Blk88GT]

Thanks for the info, I had no idea you could bend copper like that!

 

[djjsr]

You can safely use M copper. It will easily withstand the pressure of any garage compressor. Reference the tables at Copper.org.

 

[ddawg16]

Copper is a nice way to go....I have M in mine.....no issues.

 

[sublimate]

Note that the copper.org handbook recommends brazing, not soldering, for compressed air lines.

 

[G_P]

Type L is also rigid tubing.

I've used type M up to 125psi soldered with standard plumbing solder with no problems.

Buying rolls of copper tubing is going to be a lot more expensive than using rigid tube and fittings. Buy fittings at a big box store. Small hardware stores tend to have insane high prices on fittings.

Sent via carrier pigeon.

 

[Sokoloff]

Or buy fittings at pexsupply.com (no affiliation, just a hack homeowner and very happy pex supply customer)

 

[Lhorn]

Pretty sure mine is M. Got it at Lowes I think. Soldered joint. My pressure is limited to less than 100 psi just because that's what I need.

 

[flat350]

Copper is normally priced the same per foot to the wholesaler be it in 20' hard lengths or soft rolled, 1/2" L hard would be the same $ as 1/2 L soft.Type K is difficult to locate in hard lengths.The job will look much neater and clean using hard with fittings over soft and bending it,you'll never get the soft copper as straight as it is in it's hard form and you may find type L will withstand a little more abuse from impact than type M will.

 

[maxspeed96ct]

If it were my shop and a place id be staying long term Id use L , but there's a ton of M tubing out there that has been fine for centuries and will be fine for many centuries to come.

Just depends on you budget and long term goals.

Hell, you could even use pex if you really wanted to .

 

[Blk88GT]

I'm staying where I am forever, believe me! I'm going to use rigid M and/fittings. I'm sure it'll work just fine for my intended use. Thanks everyone!

 

[csp]

Thanks for the info, I had no idea you could bend copper like that!

Only if it's soft copper sold in a roll. Type K and L rigid can't be bent like was implied. It takes a special bender to bend rigid copper.

 

[5mall5nail5]

I am going to pick up M pipe this weekend

 

[5mall5nail5]

Also, do you guys solder or braze the sections?

 

[Blk88GT]

I soldered my last shop's air lines and will do the same for this one.

 

[djjsr]

Soldered joints are plenty strong enough to hold the pressure. Now I'm sure some "expert" will be here shortly to tell you that they could come apart in a fire. My opinion is that if you have a fire that hot, your air piping is the least of your worries.

 

[Bobdog]

Only if it's soft copper sold in a roll. Type K and L rigid can't be bent like was implied. It takes a special bender to bend rigid copper.

No it doesn't, I do it all the time. You just have to anneal the copper with a torch and let it cool down.

 

[Bobdog]

Also, do you guys solder or braze the sections?

I'd braze them, but you'll be fine with M copper and 50/50 solder.

I've seen refrigerant line sets done this way in the 50's and 60's that are still leak tight to this day and they routinely see 3x the pressure you're talking about.

 

[Kevin C]

Soldered joints are plenty strong enough to hold the pressure. Now I'm sure some "expert" will be here shortly to tell you that they could come apart in a fire. My opinion is that if you have a fire that hot, your air piping is the least of your worries.

That's why you wrap the joints with electrical tape.

 

[5mall5nail5]

I want to do K type soldered. Yeah?

 

[djjsr]

I want to do K type soldered. Yeah?

I'm curious. Why do you think you need K copper?

 

[Bobdog]

I want to do K type soldered. Yeah?

Well, if you're going run enough pressure to warrant K copper, then you'd be better off brazing or at the least using a silver bearing solder, such as Harris "Stay-Brite #8".

Additionally, if your application is going to see a lot of vibration, heat, or thermal stress then you'd better not solder it.

 

[5mall5nail5]

Sorry I intend to run the cheaper pipe I thought it was k