Comparing CPVC to steel pipe for fire sprinkler systems

CPVC insights

• CPVC is UL listed and FM Global approved for use in light hazard occupancies, making it a viable alternative to steel for fire sprinkler systems in commercial buildings.
• CPVC offers several advantages, including lower costs, superior corrosion resistance and enhanced architectural flexibility.

When assessing materials for fire sprinkler systems, it’s important to acknowledge that steel is not the only option. In fact, chlorinated polyvinyl chloride (CPVC) pipe and fittings are UL listed and FM Global approved for use in light hazard occupancies, as defined by the NFPA. That means CPVC can be used to protect schools, office buildings, hospitals and other light hazard commercial facilities.

Fire protection engineers understand the key objectives of sprinkler system design to protect people and property. When designing systems, risk management is always a top issue during project planning and when it comes to choosing materials. There is a widespread misperception in the engineering community that, when it comes to sprinkler pipe and fitting material, steel is a stalwart and the sole acceptable material for commercial light hazard occupancies. However, this is not true. CPVC has been on the market since 1984 and is used in commercial light hazard settings around the world.

The misperception is likely rooted in the general understanding that CPVC is well-accepted for residential use. It is regularly chosen for high-rise residential buildings over four stories. It is not as widely known that CPVC is also a great fit for light hazard applications beyond residential applications. According to NFPA 13: Standard for the Installation of Sprinkler Systems, it can be installed in schools, health care facilities, institutional, offices and nursing home occupancies.

Engineers and system designers have been accepting of CPVC in residential light hazard applications for decades, and those systems have performed very well. It is time to take the benefits of CPVC into commercial applications to create additional value.

CPVC performance in fire

CPVC is designed for light hazard commercial applications and has passed rigorous fire performance testing to achieve its NFPA listings. For instance, BlazeMaster fire sprinkler systems are UL listed for UL1821: Standard for Thermoplastic Sprinkler Pipe and Fittings for Fire Protection Service.

The UL 1821 fire test requires that an assembly sits at a minimal distance from a 1,600 F flame, with the fire plume touching the pipe at 700 to 900 F. The nonmetallic pipe and fittings must survive these temperatures for one to three minutes, until the sprinkler head activates. After 10 minutes of continuous exposure to the flame, the assembly must pass a pressure test of 175 psi.

Figure 1: With little to no tooling needed, the flexible CPVC pipe is easily installed in tight ceiling spaces. Courtesy: Lubrizol Corporation

Another misconception is that all plastics support combustion once the flame is removed. However, CPVC requires at least 60% oxygen to support combustion. Therefore, CPVC requires more oxygen to burn and sustain flaming combustion than the amount of oxygen found in the earth’s atmosphere —approximately 21%.

Instead of burning, when CPVC is exposed to flame it develops charring on the outside of the pipe, forming a thermal barrier that restricts the flow of heat into the pipe wall. In addition, CPVC’s ignition temperature of 900 F is higher than many other building materials.

Because of CPVC’s ability to withstand fire, it is listed and approved for NFPA 13 light hazard applications under the following standards: NFPA13R: Standard for the Installation of Sprinkler Systems in Low-Rise Residential Occupancies; NFPA 13D: Standard for the Installation of Sprinkler Systems in On- and Two-Family Dwellings and Manufactured Homes; NFPA 24: Standard for the Installation of Private Fire Service Mains and their Appurtenances; and NFPA 90A: Standard for the Installation of Air Conditioning and Ventilating Systems. It also meets a wide range of ASTM standards.

Benefits of CPVC fire sprinkler systems

Compared to steel pipe, CPVC delivers a variety of benefits.

Reduced installation costs: CPVC has a C Factor of 150, compared to 120 for steel, which means designers can specify a smaller diameter pipe that is less expensive, while ensuring the same water flow.

Figure 2: CPVC’s ability to withstand fire and adherence to NFPA 13 makes it a preferred fire sprinkler system for a range of commercial buildings. Courtesy: Lubrizol Corporation

Lowered lifetime cost of the system: CPVC has a natural resistance to corrosion, scaling and microbiologically influenced corrosion. With steel pipe, corrosion eventually causes pinhole leaks that result in costly and disruptive repairs. By comparison, water and oxygen are not a problem for CPVC systems, so they deliver high-performance protection with a lower total cost of ownership than metallic pipe. In addition, steel pipe needs to be internally inspected every five years under NFPA 25: Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems. CPVC, on the other hand, will not corrode, so there are no requirements for internal inspections of CPVC systems, saving time and money.

Supports light construction methods: Many engineers and architects are using lightweight construction methods for a variety of reasons, including speed of construction and cost savings. CPVC is 40% lighter than steel, and lightweight CPVC reduces overall loads on structures. This is important as new equipment, such as photovoltaic cells adds weight to structures.

Delivers superior environmental performance: Compared to steel pipe, CPVC is more sustainable.

Enhanced architectural and design options: The use of smaller pipe offers more room above ceilings and behind walls, which offers flexibility for creative design features. While, steel requires a split ring hanger dropping from a ceiling, which limits finished ceiling height, CPVC can be fastened directly to a concrete ceiling, maximizing finished ceiling height. CPVC can be installed and embedded in non-post-tensioned concrete. It can also be installed with some radius and is more easily installed in tight spaces, which opens design options.

Limited disruption for building occupants during retrofits: Steel systems may require torches, noisy equipment and large work crews, which often limits working hours or requires occupants to vacate the site. By comparison, CPVC systems are installed with basic hand tools and a solvent cement weld process that keeps noise levels low. One person can complete an area, so there is less need to have numerous installers at the site disrupting occupants.

These benefits highlight how CPVC is a viable option for designing fire sprinkler systems for a wide range of commercial buildings. As awareness grows, more engineers will likely specify CPVC fire sprinkler systems for light hazard facilities.

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