Materials Used in Water Supply Pipes

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Updated on 10/27/24

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Materials Used in Water Supply Pipes — The Spruce

Water supply pipes used to transport potable drinking water in a home plumbing system use different materials than those used for the pipes carrying drain water. The materials used vary from metals like steel or copper to plastic derivatives like PVC, CPVC, and PEX. Your home may have a plumbing system that uses all one type of material for the water supply pipes, but don't be surprised to find several types of pipes, especially in older homes with many plumbing repairs or updates.

Here are some common materials used for water supply pipes.

01 of 05
Copper

The Spruce / Kevin Norris

Copper pipe is mainly used for hot and cold water distribution and is regularly used in HVAC systems for refrigerant lines. Although once used in gas piping, this is no longer allowed in some jurisdictions. Special features:
- Lifespan: Copper plumbing pipes can last up to 50 years, but copper thins out as it ages, eventually leading to pinhole leaks.
- Above and below-ground applications: Copper piping works in underground and above-ground applications. However, some soils can affect copper, so it should have a protective sleeve if used underground.
- Thickness and uses: Copper comes in different thicknesses—M, L, and K. M is the thinnest grade. K is used in underground applications and high-pressure situations. M is used in heating applications and isn't allowed for water lines in some jurisdictions because it cannot withstand high pressure.
- Connectors: Copper can be connected in different ways, including compression fittings, push-fit fittings, or sweat-soldering.
Though copper pipes and fittings are still widely available, the price of copper and the labor-intensive attention needed to install them have caused many builders to switch to PEX. However, depending on where you live and whether you are commercial or residential, copper may still be used widely over plastic alternatives.
02 of 05
PEX

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PEX (cross-linked polyethylene), sometimes called XLPEl, is high-density polyethylene commonly used for hot and cold water lines in homes and hydronic heating systems (such as radiant under-floor systems). It is also resistant to both hot and cold temperatures. Most plumbers prefer PEX tubing over copper and other plastics for water supply pipes. Special features:
- Lifespan: PEX is considered more durable than copper, with a lifespan likely more than 50 years.
- Cost and ease of use: It is inexpensive and comes in long rolls that are easy to transport. Because the flexible tubing can be bent around corners, fewer elbows and other fittings are required, speeding up installation.
- Connectors: PEX can be joined in many ways, including push-fit fittings and crimp rings secured with specialty PEX tools.
03 of 05
Galvanized Steel

The Spruce / Kevin Norris

Galvanized steel pipe was once the most common type for water supply lines. If you have a house from before the 1960s, you may still have galvanized water lines. They are treated with a galvanized zinc coating to prevent water from corroding them.

Because of the intense labor and time involved in cutting, threading, and installing galvanized pipe, it is no longer used much except for repairs. However, galvanized pipe for water distribution is still used in larger commercial applications. Special features:
- Lifespan: According to home inspection agencies, galvanized piping has a functional life of about 40 years. An upgrade is probably advisable if your galvanized steel plumbing system is approaching that age.
- Connectors: If the pipes are still in good condition, hardware stores carry a variety of fittings and can cut and thread galvanized pipes to match your needs.
04 of 05
PVC

The Spruce / Kevin Norris

PVC, or polyvinyl chloride, is a plastic pipe used for waste water drainage and is not considered safe for drinking water. PVC is also very common in pool and spa systems. Special features:
- Lifespan: PVC pipes can last 50 to 100 years; recent advancements in new ones last the longest.
- Color system: This pipe is often white but can come in other colors. For example, a purple pipe with black lettering is sometimes used for reclaimed water.
- Thicknesses: It comes in various thicknesses or "schedules." Schedule 40 is common for pipes used in water distribution.
- Connectors: PVC connections are made using a primer that softens the PVC, and PVC glue is applied to melt the joints and pipe together. In commercial applications, all piping systems are labeled.
Continue to 5 of 5 below
05 of 05
CPVC

The Spruce / Kevin Norris

CPVC, or chlorinated polyvinyl chloride, is used for transporting hot and cold water and is safe for drinking water. Depending on its thickness (schedule), it can withstand temperatures up to 180 degrees Fahrenheit. CPVC pipe should always be clearly labeled for potable (drinkable) water. Special features:
- Lifespan: According to the International Association of Certified Home Inspectors (InterNACHI), CPVC and PVC pipes generally last 50 to 80 years under perfect conditions. However, early failure is also reported in some circumstances.
- Connectors: As with PVC, you should use primer and glue when making a CPVC joint. Also, ensure the glue specifies that it can be used on CPVC.
- Color: It is often (but not always) cream-colored or off-white plastic.

Other Household Water Pipes

You may encounter other household plumbing pipes, such as ABS, cast iron, black steel, and flexi pipe. These are not usually used for transporting drinking water but may be used for draining waste water, sprinkler systems, or appliances.

ABS (Acrylonitrile butadiene styrene) pipe: This pipe is made of thermoplastic resin and looks much like a PVC pipe, except it is black and slightly softer. It's mainly used as a vent and drain line for indoor and outdoor plumbing. When used indoors, restrict the pipe to drain, waste, and vent (DWV) applications.
Polyethylene: This generic pipe material differs from PEX or crosslinked polyethylene because its molecules are not crosslinked, high-density, or as strong as PEX's. It should only be used for cold water applications and is a good option for outdoor water supply.
Cast iron: This rigid, dark gray piping is often used for sewer and other drainage purposes. It is still found in many homes and is used today in commercial and high-rise building applications. Cast iron is expensive but durable and has good longevity. It's viable until it rusts completely. It's also cumbersome and difficult to cut. Retrofits tend to replace cast iron pipes with rigid plastic pipes, such as ABS.
Black steel: This metal pipe is commonly used in commercial and residential plumbing projects. It is made from hot-rolled or cold-rolled carbon steel that has been blackened to resist corrosion and rust better. It is used to carry natural gas into homes and businesses since it is seamless, making it stronger and safer. Black steel pipe is also used for fire sprinkler systems because it is more fire-resistant than galvanized pipe.
Flexi or braided pipe: Flexible pipe, often called flexi for short or braided pipe, is flexible tubing typically made of stainless steel. It's commonly used for water heaters, toilets, and sinks and comes in many lengths and sizes. It's somewhat durable, though it commonly fails after years of wear and tear, so it's generally not permitted for use inside walls or floors. It also is expensive, though you typically don't need much of it for a project.

FAQ

What is the best type of pipe for residential water lines?

PEX tends to be the plumber's favorite material for water supply lines because of its flexibility, low cost, and longevity. PVC remains the top choice for water drainage.
Which is better for water lines, PEX or PVC?

Choose PEX to bring and transport potable water within the home. Choose PVC to drain away waste water.
What is the best type of pipe to use for an outdoor water line?

Generic polyethylene piping works great for an outdoor water line that only carries cold water. It's flexible, durable, potable-water-safe, and inexpensive.

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