I'm running 1/2 inch "L" copper to plumb my bathroom. I was intending to use the same pipe for the risers and stubs, which will connect to shutoff valves with compression fittings.

I was going to use the standard Brasscraft valves available from HD. Someone told me that I can only use these types of valves with "M" copper.

Is this true? Should I buy some M pipes just for the stubs?

2 Answers 2


Compression style stops work the same on Type M and Type L, they both have the same outside diameter (O.D., 5/8").

Type M is thinner walled and (IMO) substandard. It is cheaper for a reason, you should use Type L.

As a sidebar: it seems you are familiar with soldering since you are plumbing the bathroom yourself, so why would you use compression (or "Sharkbite") connectors? It will just set you up for difficulty when (not if) the stops start to leak-by later on and you have to replace them. Solder male adapters to your stub-outs and use thread-on stop valves.

  • Thanks! I agree about L vs M. I chose comp valves instead of sweat because I didn't want to risk frying the innards of the valves... I didn't even think about threaded adapters! Thanks for the idea :)
    – bitsmack
    Jan 29, 2018 at 4:59

The outer diameter of the various pipe qualities and wall thicknesses is all the same. Let me recommend Shark Bite as opposed to the compression. It is more reliable.

  • Nominal thicknesses may indeed be the same, but my understanding is that the various types are held to a higher or lower standard of consistency. This means that Type M can have thinner sections in its wall than other types.
    – isherwood
    Jan 29, 2018 at 2:48
  • Brain cramp. The wall thickness will clearly change. It is the outer diameter that remains the same.
    – Paul Logan
    Jan 30, 2018 at 2:40

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