How to Determine Copper Pipe Type in Older Homes

Knowing what type of copper pipe is installed in your home will help you identify the uses of the pipes as well as assess whether the pipe is the right type for the job. Copper pipe is available in four distinct types: "L," "M," "K" and "DWV." The primary difference between types of copper piping is the thickness of the pipe wall. The different types of copper pipes are identified by the colored striping painted on the sides of the pipe. Even in older homes, you should see some color on the pipe to help identify its thickness.

Flashlight

Instructions

- 1
  Go into the basement, crawl space or utility access area where the copper pipes are exposed. Use a flashlight to see into dark areas around pipes.
- 2
  Look around the pipes for blue paint. Blue indicates the pipe is type "L" copper, which can be used in above-ground plumbing applications and below-ground drainage and ventilation systems.
- 3
  Look around the pipes for red paint. Red indicates the pipe is type "M" copper, which has a thin wall and is used in most residential water systems. This type of copper should not be installed underground, however.
- 4
  Look around the pipe for yellow paint. Yellow indicates the pipe is for "DWV," or drainage waste and vent systems. This type of copper should not be installed underground, and is not rated to carry potable drinking water.
- 5
  Look around the pipe for green paint. Green indicates the pipe is type "K," which is the thickest of all copper pipes. Because it is so durable, type "K" pipe can be used in natural gas systems, fire sprinkler systems, and underground irrigation and sewer systems. Type "K" pipe is the longest lasting of any copper pipe.

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