From Type K to DWV
For many newer home installations, copper pipes are being replaced by flexible PEX (cross-linked polyethylene) given that PEX is much less expensive and not as prone to freezing, but copper pipes are still sometimes used as they are considered an extremely strong building material that has a longer lifespan of up to 70 years.
Not only are there different types of copper pipes, but the types are indicative of the pipe’s strength and application. Knowing the four main types of copper piping can ensure that you’re installing the right kind for your home and that your pipes will last you for decades to come.
Type K copper pipes are durable and made to last, due to their thick walls. The thickness of Type K pipes can vary based on the individual pipe’s diameter: for instance, ½-inch Type K pipe has a wall thickness of .049 inches, while ¾-inch has a thickness of .065 inches. Because this type is thicker and heavier, it’s also more expensive, making it a good choice for projects that require heft, such as commercial plumbing, HVAC, city water mains, and underground lines. Type K is available in flexible and rigid forms, and is usually identified by a green stamp.
Best for: City plumbing projects and other underground lines
Considered the most common type of copper piping, Type L copper pipes are often used for interior plumbing, swimming pools, some HVAC projects, and fire protection. These pipes are less expensive than Type K pipes, but are still very strong, with a wall thickness of .045 inches for a ¾-inch diameter. Type L copper pipes are marked with blue and come in both flexible rolls and rigid tubing. If your area has hard water, Type L is a good choice as the minerals won’t wear away at the thicker walls as easily as Type M pipes.
Best for: Interior plumbing, swimming pools and spas
Identified by red markings, Type M is the thinnest copper pipe listed here, with a wall thickness of .032 inches for a ¾-inch diameter pipe or .028-inch thickness for a ½-inch diameter pipe. Type M copper piping is often used for repairs, replacements, and extensions to interior water supply lines (if you need to fix a copper pipe leak, for instance); it is less rigid and easier to work with than pipes with thicker walls, making it a favorite of DIYers. It is also less expensive but is not always allowed by plumbing codes, so check with your local building authority or a local plumber before installing it.
Best for: Repairs or replacements to home water lines, where allowed
DWV stands for “drain-waste-vent”—as that suggests, these pipes are used exclusively in drain and vent lines. You won’t find copper DWV piping in newer homes; many contemporary construction projects rely on ABS plastic or PVC pipes vs. copper. Copper DWV pipes are only suitable for above-ground applications, and are never used in water systems as they only have a wall thickness of .042 inches for a 2-inch pipe and can withstand just 15 psi of pressure. Copper DWV pipes are marked with yellow.
Best for: Drain-waste-vent pipes for exposed locations or vintage homes that require piping to be consistent with historical choices
| Copper Pipe Type | Durability | Uses |
|---|---|---|
| Type K | Very strong with thick walls | Main water lines, oil, HVAC |
| Type L | Strong with thick walls | Many applications, often used for interior water lines |
| Type M | Less strong, with thinner walls; not allowed in every municipality | Repairs and replacements for interior water lines |
| DWV | Thin, incapable of handling high pressure | Only used for drain-waste-vent piping |
