When to use Type L and Type M copper pipe
1 of 1Type L and Type M copper pipe
Type L copper pipe
is recommended where you need strength and
protection. But for normal “in the wall” household
plumbing, Type M copper pipe is just fine.
You may be surprised to find two types of copper pipe on the home center shelf, Type L and Type M. The difference is the wall thickness of the pipe and
therefore the pressure it can handle. The exterior
dimensions are identical, meaning you use the same
copper fittings. You also use the same tools, materials
and techniques to cut and sweat them. The beefier
Type L is often used underground, in hot water
heating systems, for commercial plumbing and for
gas line (where permitted). Most plumbers use the
less-expensive Type M for residential projects: One
told me, “Type L pipe will last 300 years and Type M
only 250.” But check with your building inspector;
some areas require Type L.
Acidic water with a pH of 7 or less can be hard on
copper pipe. If you have a well and find out from
testing that the water is acidic, you may want to use
the thicker-wall Type L pipe; better yet, use “plastic”
CPVC pipe and fittings. Note that most “city water,”
even in areas of the country where the water is acidic,
is balanced to eliminate this problem.
But according to veteran plumber Charlie
Avoles, the best alternative to copper is PEX (flexible
plastic pipe). “We’re seeing that many properties of
PEX are actually tougher than copper, and PEX doesn’t
appear to get fragile with age and exposure to ultraviolet
light like CPVC does.”
