A comparison of plumbing pipe types explains which offer performance, reliability, and cost savings for different systems.
By Jonathan Simon
There are multiple differences between the major plumbing systems in use today, and those differences can have a direct effect on profitability and reputation. Let’s review four areas where the differences matter most—but first, here’s a quick review of the systems available:
- Copper: a traditional piping material, not used as often in modern residential projects due to high installed costs
- CTS SDR 11 CPVC: typically tan in color and sold from ½-inch to 2-inch diameter, commonly used for mains and risers in smaller projects and for partition piping
- IPS Sch. 80 CPVC: typically gray in color and sold at diameters from ½ inch through 24 inches, a thicker pipe typically used for risers and mains in larger projects
- PEX: can be red, blue, white or clear, flexible copper tube size SDR 9 piping generally used in small-diameter applications
Compatibility with Local Water Conditions
It should be safe to assume that any residential plumbing system can perform reliably in all water conditions that meet U.S. EPA standards, but that’s not the case. Copper and PEX can both be susceptible to premature failure due to incompatibility with local water conditions, which can lead to significant litigation. In fact, a top 30 builder recently settled a class action lawsuit that claimed the copper plumbing used in a development failed prematurely because the pipes “were defective for the water conditions present.”
In some cases, these incompatibilities are documented. In Technical Note 53, the Plastics Pipe Institute (PPI) identified multiple conditions that can accelerate chlorine degradation in PEX plumbing systems, including:
- Temperatures over 140°F
- Pressures over 80 psig
- Oxidative reduction potential of the water, (which is heavily influenced by chlorine-based disinfectants)
In addition, most warranties from PEX and copper piping manufacturers contain exclusions for damage to the system caused by water conditions, meaning the warranty does not cover damage caused by chlorine dioxide in the water running through the pipe. CPVC is the only plumbing material that is 100 percent immune to degradation or corrosion from chlorine, chloramines, and chlorine dioxide in drinking water.
Impact on Water Pressure and Flow
The type of fittings used in a plumbing system has a direct effect on flow and pressure. With PEX insert fittings, the fitting reduces the internal diameter of the pipe at the fitting, creating a larger pressure drop than the socket-style fittings used by copper and CPVC. Even expansion PEX fittings have a much smaller internal diameter than a CTS SDR 11 CPVC fitting. For example, in a ½-inch 90-degree elbow, a PEX expansion fitting can create a pressure drop up to six times that of a FlowGuard Gold CPVC fitting.
When designing systems that feature multi-fixture luxury showers, this difference is amplified as these showers can require eight or more fittings to balance the flow and pressure within and across the various loops in the system. With the pressure drop created by each insert fitting, the only way to ensure sufficient pressure when using PEX is to upsize piping in the loop and the upstream branch line. Upsizing is not typically required with copper and CPVC.
Speed and Cost
Both PEX and CPVC present affordable alternatives to copper, and CTS SDR 11 CPVC is generally less expensive than PEX. It’s easy enough to check the relative costs for these systems for a given project.
Installation speed is a little trickier to navigate as many plumbing system manufacturers claim fast installation, and plumber preferences and skill level play a role in installation speed. However, the NAHB’s Home Innovation Research Labs conducted a controlled time study of the installation speed of PEX and CPVC. That study found that CPVC installed about 15 percent faster than PEX in trunk-and-branch configurations, and PEX installed 10 percent faster than CPVC in mini-manifold configurations. The study did note that the material costs associated with mini-manifold designs offset time savings.
Proven Reliability
It can take decades for plumbing system reliability issues to surface as the industry found out with polybutylene, which became popular in the 1970s and 1980s, but then had to be taken off the market due to a large number of chlorine-related failures and the class-action lawsuit that resulted from those failures.
Water compatibility issues are one of the key causes of premature failure, so systems like CPVC that are immune to damage from chlorinated drinking water eliminate a key cause of failure. Fittings are another area of vulnerability in some systems. More complex, multi-part fittings create more failure opportunities than the simpler two-piece fittings used by CPVC and copper systems. The CPVC solvent weld process chemically fuses the fitting and pipe into a single piece of CPVC that is stronger at the fitting than the pipe alone.
CPVC has been used for American drinking water systems since 1959, and both CTS SDR 11 CPVC and IPS Sch. 80 CPVC have proven themselves through the years as the only systems capable of standing up to the full range of aggressive water conditions found in the U.S. and Canada. Where other materials can fail in chlorinated water, even when properly installed and serviced, CPVC pipes and fittings stand the test of time.
Making the Right Selection
With its inherent compatibility with U.S. water systems, fast and easy installation, and socket-style fittings that minimize pressure drop, CPVC delivers the performance, reliability, and cost savings professional plumbers appreciate.
About the Author
Jonathan Simon is the North American residential plumbing manager for Lubrizol Advanced Materials Inc., the parent company for FlowGuard Gold Pipe and Fittings. For more information on FlowGuard Gold CPVC or to download sample specifications, visit FlowGuardGold.com.
