The Right Pipe for the Job

Plumbing pipe can be made from a variety of materials, each having its advantages and disadvantages depending on the situation. Some types of pipe are intended for only one application (e.g. black iron for gas), while others can perform several. What's best for your building depends on numerous physical factors, preferences, and above all, local code. Curious about your options? Here's some basic info.

Water Service

The service line is the one that goes between the provider's water main and the home/building. Because it lies within the property lines, it is the owner's responsibility.

• Copper and plastic are the typical options for a service line. Older buildings may have galvanized steel, cast iron, or even lead pipes.
• When copper is used, it's not usually rigid pipe, but a roll of continuous tubing that's run to the house. With the only joints being at the two ends of the run, the risk of leaks and breaks is reduced. In the right soil conditions (copper is sensitive to low soil pH and high levels of sulfates and chlorides), the only knock against copper is its price.
• As you probably know, copper comes in different types, based on wall thickness. Though many distribution systems use the relatively thin-walled type M, water service requires the thicker walls of type L or K. Some areas allow only for type K to be buried.
• High-Density Polyethylene (HDPE, often just "PE") has become one of the most popular choices for underground service lines, thanks to its corrosion-resistance, durability, and competitive price. Some codes require that buried plastic lines under 2" in diameter be PE (rather than PVC).
• PVC (Polyvinyl Chloride) is another plastic option for service lines. Usually found as part of a DWV or irrigation system, PVC is approved for underground use, but not indoor distribution. It is a perfectly viable alternative to copper or PE, and is often the least expensive option.
• When a PVC service line is installed - and in some PE installations - sand or gravel is required for bedding and backfill, as the plastic on its own cannot be trusted to hold up against the weight and pressure of being buried directly in soil. Code will often dictate the type and size of the material. Some codes will require specific bedding and backfilling for metal pipes, as well - make sure your installation is following the appropriate guidelines for your area.
• While your plumber should be well aware of any local requirements, it's always a good idea to check with local authorities before work begins - some codes specify the type of pipe material allowed based on the length of the service line, the incoming pressure, or other factors.

Water Distribution

Distribution pipes run inside the structure, delivering water to fixtures directly from the cold water supply, and by way of the water heater.

• Historically, distribution has been handled primarily by galvanized steel, cast iron, and copper. Plastics have become extremely popular in recent years, while galvanized and cast iron have become increasingly rare.
• Galvanized distribution is rarely used today, and most pipe that's still in use is over 50 years old. It's usually replaced with something else when problems are encountered, owing to the numerous issues that come up when the zinc layer has eroded. Old galvanized pipes can also be a serious lead risk when a water supply is particularly corrosive.
• Price is usually the determining factor in the choice between copper and plastic, with the latter gaining popularity as copper prices rose. Copper is widely seen as a more premium material, and though it's always more expensive than plastic, it's often the first choice for any system.
• As mentioned above, type M copper is a popular choice for residential distribution. The thicker-walled type L pipe is sometimes used when there are corrosion concerns, or to help reduce vibration and pipe noise.
• CPVC is a plastic pipe similar to PVC, with the added benefit of chlorination. The different manufacturing process yields a pipe that's more heat-resistant (up to 200°F), and thus approved for indoor water distribution. Cheaper than metal and relatively easy to install, CPVC is also resistant to corrosion. When copper proves too expensive or conditions are potentially corrosive, CPVC is an excellent alternative.
• For many, it's PEX (cross-linked Polyethylene) that has become the plastic of choice in recent years, owing to its cost, ease of installation, and service record. Although it has had it's growing pains, it has affirmed its place in the pantheon of preferred plumbing materials. Its flexibility and temperature-resistance give PEX an advantage over rigid CPVC, which can more readily burst in freezing temperatures.
• To save energy and water, be sure that water lines are well-insulated (some codes even require this). On hot water lines, this limits the amount of heat lost (especially with copper, which loses more heat than plastic). On cold lines, it provides some protection against freezing temperatures that can lead to burst pipes (always remember to winterize in cold climates, as well).
• Proper pipe size is key to ensuring performance and longevity in a plumbing system. Determining that size can be complicated, which is why most of us pay plumbers. Being aware of and upfront about your water usage habits and preferences can help eliminate problems and annoyances down the road. If you're considering designing any part of a plumbing system, or making large-scale repairs, we recommend obtaining a copy of the Universal Plumbing Code book and consulting with local authorities.

Drain-Waste-Vent (DWV) System

The DWV system is comprised of a building's drain lines and vent piping. Drainage pipes carry wastewater to sewers, while the vent system removes noxious gases and allows air into the drain pipes.

• Older DWV systems are largely cast iron, with some incorporating galvanized steel and even clay pipes (for the main drain line). As noted above, the metals can be susceptible to corrosion and other problems. Copper is an approved material, but is rarely used (owing to its cost). Beginning around the 1970s, plastics became a popular alternative to these materials - a trend that continues to this day.
• Though cast iron has fallen out of favor since the advent of more affordable plastics, it does offer one chief advantage over other DWV materials: it's very "quiet". The density and thickness of cast iron pipe blocks noise from the flow of wastewater, and helps reduce pipe vibration. For those particularly sensitive to noise, cast iron is definitely worth considering.
• Among plastic pipe, the choice between PVC and ABS (Acrylonitrile-Butadiene-Styrene) is largely decided by location: PVC is more common on the east coast, ABS on the west. DIfferences between the two are negligible for DWV applications, with perhaps a slight advantage going to ABS for its one-step installation (it requires only solvent cement, where PVC requires a pre-treatment of primer).
• There's a lot to consider when installing or repairing a DWV system: pipe size, slope, cleanouts, and so on. Not to mention the fact that the stakes are that much higher when dealing with waste vs. clean water. Those without prior experience are well advised to seek out a plumber: the risk of cross connections and contamination is very real, and making a mistake is all too easy for anyone unfamiliar with code and best practices.