CPVC: A Smart Alternative to Steel Fire Sprinkler Systems
Understanding the Economic and Performance Benefits
By Matthew Kuwatch
Since 1984, more than 191,000 miles of chlorinated polyvinyl chloride (CPVC) fire-sprinkler pipe and fittings have been installed in various commercial and residential applications.
First used in water distribution systems in 1959, CPVC piping systems have quickly grown in popularity because of their fast and easy installation process, which allows contractors to meet tight deadlines and even tighter budgets.
Found in high-rise buildings, hotels, college dormitories, healthcare facilities and single-family homes, CPVC has proven to be a highly effective alternative to steel pipe in residential and light-hazard, wet sprinkler systems in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems; NFPA 13D, Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes; and NFPA 13R, Standard for the Installation of Sprinkler Systems in Residential Occupancies up to and Including Four Stories in Height.
Lightweight CPVC piping systems are approved for stand-alone and multipurpose sprinkler applications in concealed and exposed settings. They also meet the requirements of all major model building codes. They are listed by the Underwriters Laboratories (UL), UL of Canada and the Loss Prevention Certification Board. In addition, CPVC pipe and fittings are approved by Factory Mutual Global. Each manufacturer of pipe and fittings is required to pass numerous tests to receive these listings and approvals.
To understand why CPVC is garnering greater market share in the sprinkler industry, it is important to understand what makes it unique.
Durability & Long Service Life
CPVC pipe and fittings have a natural immunity to scale, corrosion and microbiologically influenced corrosion. This immunity leads to a long, low-maintenance service life that can exceed that of metallic systems. The life expectancy of steel varies, depending on corrosion factors and other environmental considerations.
CPVC systems have a 50-year life expectancy with a safety factor of two. CPVC pipe and fittings are rated for continuous service of 175 pounds per square inch (psi) at 150 °F. As part of the UL Listing requirements, the pipe is required to sustain 5 times the maximum rated pressure of 175 psi, which is 875 psi, for a period of 1 minute.
Superior Hydraulics
The Hazen-Williams C-factor is used to describe the amount of friction loss that is encountered when water flows through a pipe. Steel pipe has a C-factor of 120 compared to the 150 C-factor of CPVC pipe. This higher C-value indicates that CPVC pipe has less friction loss, which often allows for pipe downsizing of at least one size smaller in diameter than steel.
Flame & Smoke Resistance
Compared with other nonmetallic piping, CPVC is not combustible and will not contribute to flashover.
CPVC piping systems have a flash ignition temperature of 900 °F, depending on the manufacturer. This is the lowest temperature at which sufficient combustible gas is evolved that can be ignited by a small external flame. Many other ordinary combustibles, such as wood, ignite at 500 °F or less. As a result, CPVC fire sprinkler systems cannot be the ignition source of a fire.
CPVC piping systems also will not sustain burning. It must be forced to burn due to its exceptionally high Limiting Oxygen Index (LOI) of 60. LOI is the percentage of oxygen needed in an atmosphere to support combustion. Because the earth's atmosphere is only 21% oxygen, CPVC pipe and fittings will not burn unless a flame is constantly applied and stop burning when the ignition source is removed. In comparison, the LOI of cross-linked polyethylene (PEX) is 17.4.
Additionally, this type of fire sprinkler piping system also has low smoke toxicity. Testing at the UL of Canada has shown that CPVC pipe produces only one-third the smoke of kiln-dried wood.
Because it offers outstanding resistance to fire and low smoke generation qualities, CPVC fire sprinkler piping systems are even approved for use in plenum spaces in accordance with NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems.
Greater Productivity
Unlike metal systems, which have fallen victim to skyrocketing prices over the last few years, CPVC pipe and fittings are not a limited natural resource subject to international supply and demand fluctuations. This means CPVC piping systems have a more controlled, stable material cost than metal piping.
Additionally, CPVC piping systems are easier to install than metal systems. Field fabrication is quick, simple and clean, and the pipe is lightweight and easy to handle and transport.
Installation is fast, thanks to the system's one-step low volatile organic compound (VOC) solvent cement joining process. It essentially involves two operations: cutting the pipe and applying the solvent cement. Typically, by nature of the joining process, CPVC joints are actually stronger than the pipe or fitting alone.
Solvent cement set and cure times are a function of pipe size, system test pressure and temperature. For instance, when using 100-psi test pressure in temperatures between 60 °F and 120 °F, the cure time for 1-in. pipe and fittings is 15 minutes.
During retrofits, CPVC offers the following advantages:
- Quick installation means less downtime.
- Quiet and clean installation process decreases disruption to occupants.
- Design flexibility allows CPVC piping systems to be installed on walls or ceilings or even tight spaces.
Hangers & Supports
Some contractors have expressed concern about the need for additional hangers for CPVC piping systems. As pipe diameter increases, pipe becomes more rigid and requires fewer hangers. Smaller sizes around 1 inch require support every 6 to 7 feet. For steel, pipe hangers are required at about twice that spacing for smaller diameters. But, with larger CPVC pipe, there is less of a differential. The additional cost is nominal compared to overall labor and cost savings.
Most UL-listed hangers designed for metal pipe are acceptable for use with CPVC pipe. Keep in mind that no damaging sharp edges come into contact with the pipe and also that CPVC pipe needs to be free to move to allow for expansion and contraction.
Residential Installations
In the past, sprinkler systems primarily have been installed in commercial applications, while smoke alarms figured prominently in residential settings. Eighty percent of fire-related deaths, however, occur in homes. Studies have proven that installing both smoke alarms and a fire-sprinkler system reduces the risk of death in a home fire by 82% vs. having neither system installed.
Sprinkler installation in new homes is affordable - typically only about 1 to 1.5% the cost of new home construction. According to the Home Fire Sprinkler Coalition, should a fire occur, homeowners can expect financial losses up to 90% lower than in homes without an installed fire sprinkler system. The average property loss in a sprinklered home is $2,200; in a home without sprinklers, losses average $45,000.
Contrary to popular belief, residential fire sprinklers do not compromise a home's aesthetics for the sake of safety. Residential sprinklers are small and can be recessed into ceilings or walls. Some models are completely concealed by plates that can be matched to room paint colors.
Versatility
In both residential and light commercial applications, CPVC fire-sprinkler systems are commonly used in concealed installations. The minimum requirements, as set forth by UL, for concealed installations protecting CPVC are as follows:
- 3/8-in. thick gypsum wallboard.
- Suspended membrane (drop-in) ceiling with tiles weighing no less than 0.35 pounds per square foot.
- 1/2-in. thick plywood.
CPVC pipe and fittings may be installed in ordinary hazard rooms that are up to 400 sq. ft. if the building is otherwise classified as light-hazard occupancy. The listing requirements for CPVC pipe and fittings must be followed in such a room.
In light-hazard (NFPA 13) or residential (NFPA 13D and 13R) occupancies, another installation option is that CPVC systems may be installed exposed. An exposed installation refers to areas where the pipe and fittings are not behind a protective barrier as mentioned previously and are literally open to the area intended for protection by the sprinkler system. CPVC pipe and fittings may be installed in this manner (without protection) when certain standard measures of fire protection (sprinklers) are present.
When it is installed exposed, the CPVC must be beneath a smooth, flat, horizontal ceiling. Quick response sprinklers must be used. Standard coverage, residential or extended coverage sprinklers may be used. There are specific requirements for each type of sprinkler as to the sprinkler spacing, the sprinkler temperature rating and the location of the deflectors. These requirements are contained in the installation manual that is provided by the CPVC pipe and fitting manufacturer.
Conclusion
Because of these superior performance capabilities, CPVC pipe and fittings are the only nonmetallic system permitted for use in a standalone system or installed in an exposed environment, in accordance with the NFPA.
No material is compatible in all environments. Metal corrodes in salty environments. CPVC can be damaged by contact with certain chemicals found in some construction products. For instance, CPVC is not compatible with edible oils, petroleum- or solvent-based sealants, synthetic oils or glycol-based antifreeze. Incompatible materials may compromise the integrity of the CPVC piping system.
Bear in mind, however, that not all CPVC fire sprinkler pipe and fittings are the same. Because the compounds used to make CPVC pipe and fittings are derived from different base resins, performance is not necessarily consistent among products.
Some CPVC resins and compounds are developed specifically to optimize performance for individual applications. They also may be designed to meet or exceed existing code and approval requirements.
Although CPVC pipe has not been approved for use in all environments, it has proven to be a highly effective alternative to metal fire-sprinkler systems in light-hazard and residential occupancies.
This material has demonstrated, through both laboratory tests and actual installations, to offer greater cost efficiencies -- providing end users with a system that is both cost effective and reliable.
Matthew Kuwatch is the global marketing manager for BlazeMaster CPVC Fire Sprinkler Systems and the executive director and vice chair of the Steering Board for the Ohio Fire Safety Coalition. He is a member of the National Fire Protection Association, American Fire Sprinkler Association, International Fire Sprinkler Association, Society for Fire Protection Engineers and the Home Fire Sprinkler Coalition.