# Type L or M copper



## bob22 (May 28, 2008)

try google; I did and got this site with a lot of discussion of use by application:
http://www.businesshistorybooks.com/business-consulting/copper-pipe-type-l-or-type-m-694538-2.html


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## BlueBSH (Oct 29, 2009)

bob22 said:


> try google; I did and got this site with a lot of discussion of use by application:
> http://www.businesshistorybooks.com/business-consulting/copper-pipe-type-l-or-type-m-694538-2.html


that's what I did last night and all I ended up was even more confused... with people saying stuff like L is for underground only, use M then another place use L for potable M is for sprinklers..... everyone contradicts themselves... then one place says M is for under 100 psi but then I found a place sayign its for 700 psi and below :huh:


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## Bob999 (Mar 4, 2010)

The difference is thickness of the wall of the pipe. You should check local codes to make sure there is no special requirement in your area. Subject to the code, if your water is non-corrosive you can get by with M--the thinest wall. If your water tends to be a bit corrosive then L or K--the thickest wall is recommended. Alternatively you might consider using CPVC which is not affected by corrosive water and is approved by most, if not all codes and can be used for both hot and cold domestic water lines.


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## bob22 (May 28, 2008)

BLue,
I would bite bullet $wise and use the thicker walled. No harm and peace of mind.


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## TheEplumber (Jul 20, 2010)

4 grades of copper pipe- listed thickest pipe wall to the thinest.
K - green lettering, usually used for underslab
L - blue lettering. "commercial grade" most commonly speced by enginneers
M - Red lettering. "residentual grade". not used underground
DWV - Yellow lettering. Not approved for presure piping. Waste and vent only
K,L,and M are all OK for above ground domestic water inside a home.
The OD's are all the same


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## wellcraft (Nov 20, 2010)

k and l would be fine. m is used primarily for heating. since it is thin walled it radiates the heat as water travels through it. by most codes that i know of you cannot use m for domestic water useage and inspectors would frown upon it.


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## TheEplumber (Jul 20, 2010)

wellcraft said:


> k and l would be fine. m is used primarily for heating. since it is thin walled it radiates the heat as water travels through it. by most codes that i know of you cannot use m for domestic water useage and inspectors would frown upon it.


Used daily in my area


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## immeraufdemhund (Nov 17, 2010)

I find it more difficult to solder M pipe because of how thin it is, but then again I was trained using L pipe and I've primarily done commercial construction. I find though that I prefer commercial standards over residential since it is usually rated for heavier use, which means it will last longer. I don't care to spend the extra money to have peace of mind knowing that I wont have premature failure. 

Of personal experience I have found that mixing the two grades of pipe and fittings will cause problems. Maybe I had a bad batch of fittings, but when I used L fittings with M pipe there was too big of a gap and so I'd use like 2" of solder on 1/2" pipe, which made me angry. I went and bought some M fittings and that problem went away.


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## COLDIRON (Mar 15, 2009)

I have always been partial to "L" it is right in the middle and "M" seems just a bit flimsy for me . To each their own.


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## BlueBSH (Oct 29, 2009)

well in the couple fundred feet of copper pipe I finally found a piece I can read and in green print it says "3/4 IN COPPER TYPE L" weird that it's in green print, but oh well... I'll stick with the middle thickness that I have and get L copper 

are fittings like T's and curves rated on this same scale or are they universal?


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## Bob999 (Mar 4, 2010)

The fittings are "universal" in sizing because the outside diameter of M, L, and K pipe are all the same.


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## BlueBSH (Oct 29, 2009)

Bob999 said:


> The fittings are "universal" in sizing because the outside diameter of M, L, and K pipe are all the same.


well I guess I ment universal as in the specifications of the copper type like underground, pressure, etc


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