Arghhh, help me with copper pipe!

[Wood'nMetal]

I'm reworking my air compressor and air system in my shop.

My compressor head lines had been switched to flex lines but I've put the compressor and tank back together in it's original format. I wanted to replace the flex lines with rigid copper as they had come from the factory.

I read all the dire warnings about using type M copper on compressed air so I found some type L in 3/4" and managed to make the necessary bends without mutilating the pipe.

I'm in the final stages of hookup when I discovered that the 3/4" compression fittings I had waited a week for apparentely do not fit type L pipe?

What's the deal! What compression fittings do I need for type L...nowhere do I find where it says 3/4 compression fittings are only for type M.

I bought some solder on elbows for 3/4 copper and they fit just fine. I thought type L was just thicker but same o.d.

This is getting really frustrating as my shop has been without air for two weeks while I fumble with this.

 

[The Cobbler]

you need 7/8" compression fittings. that is the OD of your 3/4
type m & L have the same OD. the wall is thicker and smaller ID on type l

 

[Wood'nMetal]

Well ain't that a ***** LOL. I was just looking at the copper tube manual and it shows an average working temp of 400psi at 100 degrees with type M so maybe I'm fighting with type L for no reason!

 

[The Cobbler]

if you're bending it, M doesn't bend worth crapolla

 

[Firebrick43]

Compression fittings are "typically" used with tubing. Tubing is sized by its OD.
Pipe on the other hand is sized on it nominal(as in about, not exact) ID. The OD of 3/4" pipe is 7/8" as previously noted. Also as noted you can't bend M, only L and K. What are you using to bend it?

As far a compression fittings, why? Solder it and it's cheaper and more permanent and less likely to leak down the road. I can't say that I have actually seen compression fittings on pipe first hand, doesn't mean they don't make them.

 

[Wood'nMetal]

Have to use compression because it threads into the compressor head and chiller. Came that way factory. I could order the factory SpeedAire tubes but they want almost $200 a piece.

 

[Dagny]

I think you should use soft tubing. Hard tubing is designed to use solder fittings .

 

[Dagny]

A refrigeration co. should have what you need. ACR tubing

 

[Radix2]

I'm reworking my air compressor and air system in my shop.

My compressor head lines had been switched to flex lines but I've put the compressor and tank back together in it's original format. I wanted to replace the flex lines with rigid copper as they had come from the factory.

I read all the dire warnings about using type M copper on compressed air so I found some type L in 3/4" and managed to make the necessary bends without mutilating the pipe.

I'm in the final stages of hookup when I discovered that the 3/4" compression fittings I had waited a week for apparentely do not fit type L pipe?

What's the deal! What compression fittings do I need for type L...nowhere do I find where it says 3/4 compression fittings are only for type M.

I bought some solder on elbows for 3/4 copper and they fit just fine. I thought type L was just thicker but same o.d.

This is getting really frustrating as my shop has been without air for two weeks while I fumble with this.

Wait - why do you say they don't fit? As you note type M and L use the same fittings - do they actually fit your M ?

What kind of compression fitting do you need ?
They don't have it at the home center ?

Get a straight solder coupler and solder a short piece of M for your comp fitting?...but maybe the compression sleeves you just bought are a little undersized - try one from a different fitting.

 

[Wood'nMetal]

Wait - why do you say they don't fit? As you note type M and L use the same fittings - do they actually fit your M ?

What kind of compression fitting do you need ?
They don't have it at the home center ?

Get a straight solder coupler and solder a short piece of M for your comp fitting?...but maybe the compression sleeves you just bought are a little undersized - try one from a different fitting.

I need multiple compression fittings. The ones I have are for 3/4" but I didn't understand that tube and pipe are measured by different methods. The home centers carry up to 1/2" with a couple odd 3/4" thrown in. Looks like I will be having to go to a specialty store or just buck up and order the factory replacements. At $20 a piece for compression fittings that adds up pretty fast anyway.

 

[gnpenning]

Can you change the fitting at your compressor head to something that will convert to what is locally available?

How are you accounting for vibration with the copper at the head?

 

[Firebrick43]

I have a copper expander so I don't have to buy couplers. You just anneal and could expand an 3/4 OD "tube" to 3/4 "pipe" (7/8 OD). https://www.ridgid.com/au/en/s-tube-expander

Or you could buy these https://www.supplyhouse.com/Elkhart-20121-7-8-OD-ACR-X-3-4-OD-ACR-Copper-Coupling

Also if you still want to use tubing just know that ACR tube means it's been cleaned and sealed. I comes as straight hard sticks or in a roll. There is also type L soft tube in a roll available at many hardware stores. Same OD. You don't need ACR but many times is cheaper from a hvac supply house . However many hvac will not sell to the public. You have to be a hvac contractor.

Hard drawn copper pipe that you already have is going to be the cheapest and what I would use.

 

[Christopher1]

Using a Hacksaw. ... Though a hacksaw will cut through the copper pipe, it's difficult to hold the pipe firmly enough to get a clean cut with a hacksaw, no matter how strong you are. In plumbing, if the pipe is affixed to other plumbing when you're sawing, the excess movement can result in future joint failure.

 

[matt_i]

Personally I would have started with the softest copper. Copper is notorious for work-hardening, any vibration which causes relative motion in the pipe/tube can cause this eventually leading to a brittle fail = crack. The hard-drawn L and M pipes are already well down this path.

However in your situation, I would have tried to go from the NPT female threads of head and tank right to the tube and solder as suggested. That is a cheap $1-2 fitting you get at any home center.