[LazyPup]

Although most people are not aware of the fact, They are correct in referring to copper pipe by color code. If you examine the writing on the pipe you will find that Type K (heavy wall) will have green writing, while Type L (Standard Wall) will have Blue writing and Type M (thinwall) will have Red writing.

Both the International Residential code and Uniform Plumbing code approve all three types for both Supply & Distribution piping.

By definition, "Supply" is the direct buried line from the municipal main or well source to the structure and "Distribution" is the piping within a structure.

Under the UPC type M (thin wall) with Red writing may only be used for distribution piping only if it is above ground. (6" or higher above the slab or basement floor.)

As a rule most plumbers use type L (standard wall with Blue writing) for both supply and distribution piping.