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RESIDENTIAL: Fire Safety

 

Why PEX-based Multipurpose Residential Fire Sprinkler Systems Outperform Standalone CPVC Designs


Known for its durability and builder-friendly efficiencies, PEX tubing is installed in more than half of all new homes in the United States. As the IRC mandate for residential fire sprinkler systems approaches, builders and plumbing contractors are increasingly turning to PEX for its jobsite flexibility, installation efficiency, cost-effectiveness and overall system reliability.

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As states consider adopting the 2009 International Residential Code (IRC), which requires fire sprinklers to be installed in new homes built after Jan. 1, 2011, builders and plumbing contractors are ramping up their search for the most cost-effective and efficient fire-protection solution.

Many are turning to today’s most affordable and reliable life-saving technology: PEX-based multipurpose fire sprinkler systems. Already a mainstay in new-home construction, PEX (crosslinked polyethylene) is used in nearly three times as many new homes as rigid CPVC (chlorinated polyvinyl chloride).

Unlike standalone fire sprinkler systems created for commercial use that rely on rigid CPVC or metal pipe, multipurpose PEX-based systems combine the cold-water plumbing and the fire sprinklers into a single, efficient system. As a result, it eliminates one redundant piping system, reducing material, labor costs and jobsite-scheduling hassles, thereby saving 35 percent to 65 percent in installation time over standalone, rigid CPVC systems.1

In fact, installation costs for new multipurpose fire sprinkler systems average $0.57 less per square foot than traditional standalone systems.2 That translates into a savings of $1,368 for a 2,400-square-foot home.

"Multipurpose systems are specifically engineered for the demands of residential construction and the lifestyle of a family," explains Jayson Drake, senior product manager, Plumbing and Fire Safety, for Uponor North America. "Unfortunately, many installers cling to outdated commercial methodology and miss the efficiencies offered by multipurpose for the home."

Studies show that multipurpose PEX-based fire sprinkler systems have "the lowest cost of installation and the lowest amount of ongoing maintenance"3 for the homeowner. But lower costs are just one of the many factors behind the popularity of flexible PEX-based multipurpose systems.

INSTALLATION EFFICIENCY

In what might be the biggest advantage of all for builders, a multipurpose system needs only one subcontractor to do the work — usually the plumber already on the jobsite. This seasoned professional, typically a veteran of residential construction, is the one who combines the plumbing and the fire sprinklers into a single piping solution.

"Our existing plumber was able to install both systems at once, eliminating the need and the cost of a separate sprinkler contractor," says Emil Wanatka, president of Durango, Colorado-based Timberline Builders, which specializes in residential infill developments. "Any time you can eliminate a trade, it helps the bottom line. There are always conflicts over scheduling, training contractors to your floor plans and general worksite harmony. In our case, when it comes to subs, less is definitely more."

The reasons why PEX tubing outperforms CPVC pipe derive from the materials themselves:

  • Greater flexibility = fewer connections + less noise: The flexibility of PEX allows installers to make directional changes without the use of fittings — something not possible with rigid CPVC pipe. For example, ¾-inch PEX-a tubing4 offers a 5¼-inch bend radius. As a result, PEX can simply bend around corners and obstructions, thereby eliminating up to half the number of joints needed for rigid pipe. Said differently, an actual design comparison with CPVC found that PEX can reduce potential leak points and resulting water damage in a home by 50 percent.

    Another advantage is that because water flows more quietly through PEX tubing, it eliminates "water hammer" noises associated with rigid pipe systems. Also, PEX does not amplify sound as readily as rigid pipe.

  • Shape memory permits watertight connections: Plumbing contractors also like the thermal-shape memory of PEX-a tubing. This unique property enables installers to make watertight, leak-resistant connections without the use of potentially dangerous torches, toxic cements and solvents, or gauges.

    To make a connection, the installer uses a simple tool to expand the tubing, which quickly shrinks back around the fitting to ensure a solid, watertight connection. Installers and inspectors are easily able to visually distinguish between complete and incomplete joints. In fact, these connections actually get stronger over time and can withstand 1,000 pounds of pull tension.

    Contrast this with the common installation practice of "dry-fitting", or pre-assembling, a CPVC system before actually cementing the joints together. It can be difficult to determine if these joints have been properly cemented, so if an installer forgets to go back and apply cement to a dry-fitted joint, the incomplete connection can result in a costly leak…sometimes long after the house is finished. And an installer also has to be very careful to apply the proper amount of cement to each connection: too much can soften the inside of the pipe and lead to ruptures, while too little cement can leave gaps in the joint, also resulting in expensive leaks.

    In short, a PEX-based system is easier, faster and safer to install than CPVC and consistently results in stronger, more reliable connections.

RELIABILITY

In addition to the installation flexibility, watertight connections and cost savings that attract builders and contractors to multipurpose fire sprinkler systems, many jurisdictional authorities and homeowners prefer multipurpose designs for their reliability.

  • Easy verifiability: With multipurpose systems, homeowners cannot inadvertently and unwittingly shut off fire protection to their homes. In a standalone fire sprinkler design, the system can be turned off — for example, to perform routine maintenance — and forgotten.

    "If the shower or the toilet is working, so is the multipurpose fire sprinkler system," says Drake, who notes that standalone systems have no similar "verification," except through annual maintenance inspections. "The most common reason for a fire sprinkler system to fail is that the water is shut off — a situation that is readily apparent in a multipurpose system."

    Following installation, multipurpose PEX contractors typically check for leaks using compressed air, and verify the system’s operation by measuring the actual water volume against the specified flow rate (typically 15 to 18 gallons per minute).

    "Installers of standalone CPVC systems tend not to perform either of these simple tests," says Drake, who notes Uponor requires both to be completed. "CPVC manufacturers advise against air testing, because the material can shatter and explode. I think it’s reprehensible for any contractor to finish the installation of a life-saving sprinkler system without conducting a flow test to actually make sure that the system is operating as designed."

  • No antifreeze needed: Multipurpose fire sprinkler systems do not use antifreeze solutions, even in the coldest of climates. Because standalone systems contain stagnant water, installers typically use antifreeze mixtures to ensure proper operation in cold climates. If improperly mixed, these solutions can actually accelerate a fire and even trigger explosions. Concerns over flammability after a recent fatal incident led the National Fire Protection Association (NFPA) Standards Council to issue a Safety Alert regarding the use of antifreeze:

    1. "For now, and until any further action by NFPA consensus standards committees, NFPA sprinkler standards prohibit the use of antifreeze in new residential fire sprinkler systems."

  • Superior resistance to freezing: The warmth of a heated interior and proper insulation should allow both PEX and CPVC systems to operate as designed even in colder regions of the country. But what happens if a severe winter storm knocks out power for an extended period?

    A six-month-old home in Washington State, for example, lost power in 2009 and went without heat for four days, causing the water inside the standalone CPVC sprinkler piping to freeze and subsequently break.

    The PEX plumbing system in this same house suffered no stress fractures, however. That’s because flexible PEX tubing is more freeze-resistant and can expand when frozen, then return to its normal size when thawed — without breaking. The superior elasticity of PEX makes behind-the-wall freeze breaks much less likely to happen than with rigid CPVC pipe.

    It should also be noted that CPVC is susceptible to environmental stress cracking when it comes in contact with certain, common construction materials, such as leak detectors, thread sealants, pipe wraps, lubricants (e.g., WD-40®) and all-purpose caulks. This cracking, which can occur regardless of household temperature, can lead to leaks and, ultimately, to system failure.

LOWER MAINTENANCE

Another important distinction between multipurpose and traditional standalone fire sprinkler systems is that the latter require a backflow preventer, a check valve and/or a separate water meter.

Standalone sprinkler systems keep toxic, stagnant water out of the drinking water system with check valves or backflow preventers, adding cost and labor to these installations. To avoid contamination of a home’s potable water supply, some communities (Tacoma, Wash.) favor multipurpose designs, while others (Nolensville, Tenn.) require them and do not allow standalone.

Many states, fearing contaminated water flowing back into domestic lines, require a double check valve assembly (DC) or reduced-pressure (RP) backflow prevention valves. Besides the upfront costs for these extra components, they must also be inspected and maintained regularly. Likewise, the strength of any antifreeze mixture in a standalone system also requires an annual inspection, because antifreeze breaks down with age and must be replaced.

In contrast, multipurpose fire sprinkler systems contain only potable water and, therefore, require fewer add-on devices to maintain, inspect or fail. A multipurpose system is all but maintenance-free except for periodic visual checks.

CONCLUSION

First used in water distribution systems in the 1970s, PEX tubing systems have quickly grown in popularity because of their easy installation and durability, which allow contractors and builders to meet tight deadlines and even tighter budgets. In recent years, PEX has proven to be a highly effective alternative to CPVC pipe in residential sprinkler systems.

For the past 15 years, PEX-based multipurpose fire sprinkler systems have been listed in NFPA 13D, the sprinkler industry’s standard for the installation of residential sprinkler systems in one- and two-family homes. The International Residential Code (IRC) lists multipurpose residential fire safety systems under Section P2904, and acknowledges compliance with NFPA 13D.

PEX-based plumbing systems have a 40-year track record in millions of installations in homes and businesses worldwide. As one of the most thoroughly tested plumbing materials on the market today, PEX has proven to be the most efficient and cost-effective material for residential plumbing and fire sprinklers.


Multipurpose Sprinkler Systems: Summary of Benefits

Single-source Contractor. A multipurpose system needs only one subcontractor to do the work — usually the plumber already on the jobsite — eliminating the hassle and the cost of a separate sprinkler contractor.

Watertight Connections. PEX’s unique shape memory enables installers to make watertight, leak-resistant connections with no possibility of uncemented, dry-fitted joints. Moreover, the flexibility of PEX tubing reduces the number of connections, and potential leak points, by 50 percent.

Reliable Performance. A key benefit of these interconnected, multipurpose systems is reliability – homeowners cannot inadvertently shut off fire protection to their homes. In fact, homeowners know that water is available to their sprinklers each time they use a faucet or flush a toilet.

Cost-effective. Because multipurpose systems eliminate one redundant piping system, builders reduce material, labor costs and jobsite-scheduling hassles. These flexible systems can reduce installation time over standalone CPVC systems by up to 65 percent.

Low Maintenance. A multipurpose system is all but maintenance-free. A standalone CPVC system must have its backflow preventer or check valve professionally and regularly maintained, as well as the strength of any antifreeze. Studies show that multipurpose PEX-based fire sprinkler systems have ―the lowest cost of installation and the lowest amount of ongoing maintenance for the homeowner.3

Specially Designed for Residential. Unlike standalone fire sprinkler systems created for commercial use that rely on rigid CPVC or metal pipe, multipurpose fire safety systems are specifically engineered for the demands of residential construction and the lifestyle of a family.




1 U.S. Department of Commerce and the National Institute of Standards and Technology, NISTIR 7277 http://www.fire.gov/newsletter/fall2006/EconAnalResidSprink.pdf

2 September 2008 Fire Protection Research Foundation, http://www.nfpa.org/assets/files/PDF/Research/FireSprinklerCostAssessment.pdf, p. 11

3 "Comparison of Residential Fire Sprinkler System Service Options," Washington Water Utilities Council, October 2008. p16. A similar, 2007 study, "Benefit-Cost Analysis of Residential Fire Sprinkler Systems," by the National Institute of Standards and Technology, found that PEX-based fire multipurpose sprinkler systems offer the lowest life cycle. NISTIR 7451. http://fire.nist.gov/bfrlpubs/build07/PDF/b07025.pdf

4 PEX-a tubing is the preferred manufacturing process for producing crosslinked polyethylene (PEX) tubing because it yields the highest percentage of molecular bonding.



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