Which type of copper tube is marked with a red stripe?

• A. Type M
• B. Type L
• C. Type K
• D. Type DWV

Answer: (A)

Color and stripe markings on copper tube tell you its type and wall thickness, which in turn indicate where it’s appropriate to use and what pressure or temperature it can handle. The red stripe identifies Type M copper tube. Type M has the thinnest wall among the common potable-water tubes, which makes it the least expensive option and suitable for many standard residential cold-water applications within typical pressure and temperature limits. For higher pressure or hot-water lines, Type L (blue stripe) or Type K (green stripe) are used because their thicker walls provide greater strength. DWV copper is for drainage and isn’t used for pressurized potable water, and it isn’t marked the same way.