#103 - Residential Fire Sprinkler Systems: Guide to Installing Home Fire Sprinklers (Part 3)
#103 - Residential Fire Sprinkler Systems: Guide to Installing Home Fire Sprinklers (Part 3)
Pipe in home fire sprinklers and special components
In the last installment of our series covering the installation of home fire sprinklers, we reviewed some of the main components of residential fire sprinklers, including the water supply, pumps (if necessary), and the types of sprinkler heads that can be used and their appropriate placement. In this piece, we will round out our look at major system components, delving into a homeowner’s options for pipe in home fire sprinklers as well as the NFPA guidance and local government codes that may shape these choices.
Are you looking to buy components for a home fire sprinkler system? If so, feel free to skip directly to QRFS' selection of residential system components or use the search bar at the top of the page.
A review of residential fire sprinkler pipes
The network of pipes in a home sprinkler system can vary in both materials and the length required to cover the size of the house, making it one of the most important factors in the expense of the system.
NFPA 13D: Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes consciously gives wide latitude on the type of material that can be used, hoping to drive innovations that lead to lower costs and more frequent installation of home systems. This strategy has succeeded: Modern systems can have pipes made of expensive metals as well as less expensive thermoplastics used in modern plumbing applications, including chloro-polyvinyl chloride (CPVC) and cross-linked polyethylene (PEX).
The options include:
- Metal: Metal pipe listed for home fire sprinkler use can be made of steel, copper, or brass. The benefits of metal pipe include its durability, its ability to withstand heat and thus be exposed in areas where there may be a fire, and its higher pressure tolerance. Its main drawbacks are its expense, corrosion potential, and the internal roughness of metal pipes, which can add friction to the system. As better and cheaper options have evolved, the use of metal is getting much less common.
- CPVC (chloro-polyvinyl chloride): This commonly used plumbing pipe is also listed for home fire sprinkler use and has significantly reduced the cost of installations; the material itself is cheaper and it takes less time to install CPVC pipe than metal alternatives. It is sturdy and reliable, the joints are attached with a special glue that reduces the “sweating” seen in metal pipe, and it is resistant to corrosion. CPVC is designed to withstand higher temperatures than its cousin, PVC, but some authorities having jurisdiction (AHJ) may only allow it to be exposed in areas that could be subject to fire under specific conditions, and after being granted a variance.
- PEX (cross-linked polyethylene): This flexible tube was originally approved for multipurpose home fire sprinkler systems only because NFPA required all nonmetallic pipe to have a higher pressure threshold than PEX could handle. PEX or any other listed nonmetallic material can now be used in standalone systems, however, “if the maximum static pressure from the water supply does not exceed 80 psi” – or an automatic pressure releasing valve is used when the pressure from the water supply is higher than the limit. It is less expensive and easier to install than rigid pipe (CPVC or metal); because it can bend around corners – it also uses about half of the fittings of rigid pipe and thus has fewer potential leak points. While it cannot handle as much pressure as rigid pipe, this isn’t really an issue with home installations. Wet sprinkler system pipe should always be insulated or kept in temperature-controlled areas, but PEX can expand to three times its diameter without breaking, which safeguards the integrity of the system if a section of it is exposed to freezing temperatures.
NFPA allows the use of any of these options that are “listed for use in fire sprinkler systems by an approved [safety testing] organization” and meet pressure and flow requirements according to the hydraulic design of the system.
The water flow in a system (gallons per minute) is calculated in light of the pressure, the length of travel in the pipe, gravity, and the pipe’s diameter, and NFPA publishes these calculations for pipes ranging anywhere from 3/8” to 3” in diameter. A qualified fire sprinkler installer will work with all of these variables when designing the system.
Which type of pipe should be used?
It depends. Sometimes a combination of metal and thermoplastic pipes is used in unfinished basements, connecting to a network of CPVC pipes that run throughout the rest of the house. In certain cases, like a retrofit of an existing house where pipe needs to be exposed and run up through a closet, a contractor may use a section of metallic pipe joined to CPVC within the walls, if local authorities require the pipe to be able to withstand exposure to fire.
Generally speaking, it is advisable and becoming vastly more common for systems to exclusively use thermoplastic pipe since it is much less expensive and easier to install. CPVC pipes are the most commonly-used material, though the approval of PEX for all systems has made that material increasingly popular, especially since the flexible tubes give an installer more latitude when running it through the walls and ceilings.
The decision also hinges on whether the project is a new build or a retrofit of an existing home: The cheapest (and in some ways, most effective) option for new construction is a multipurpose system using PEX, whereas a retrofit of a standalone system may use CPVC or metal. You could retrofit a full multipurpose system into an existing home, but it will likely involve ripping open more walls and ceilings.
Special considerations for fire sprinkler pipe
Every type of pipe must be fitted and joined correctly for it to be able to withstand the system pressure. CPVC requires the application of special glue, and PEX requires fewer connections but has an arguably trickier connection process that requires crimping or clamping the tube to seat and affix it properly. Again, a qualified installer will know exactly how to do this to avoid leaks or failure.
It’s worth noting that a different form of plastic, polybutylene (PB), was used in both residential plumbing and fire sprinkler systems for roughly a decade starting in the mid-1980s. Its manufacture was ceased after concerns that “that oxidants in the public water supplies, such as chlorine, react with the polybutylene piping and acetal fittings causing them to scale and flake and become brittle.”
Thus, if you have an existing home with PB (plumbing and/or a fire sprinkler), finding replacement parts will be difficult. The failure of a portion of the system may call for a complete retrofit with different pipe materials.
Finally, if you run exposed pipe in an attic that is subject to freezing temperatures, it’s essential to properly insulate it. If the water freezes, it can break the pipe and compromise the system. Some contractors avoid having to doing this by only using sidewall sprinklers in the top floor of a home.
Other home fire sprinkler system components
The control valve
Every sprinkler system has a control valve that shuts to stop water flow and allows for maintenance or repairs to be done. A single control valve can also serve the domestic water supply and the sprinkler system, even if the sprinklers are standalone. Making sure the control valve stays open is the most important factor in whether a sprinkler system will work during a fire.
According to statistics compiled by NFPA, residential fire sprinklers only failed to deploy in 6% of fires between 2010 and 2014. In 62% of those cases, the failure happened because someone had shut off the system. Control valves need to be kept open, and the ways to guarantee it include:
- A single control valve that serves both the fire sprinkler and the plumbing. If it’s shut off, the residents will know it when the taps don’t work.
- Control valves serving fire sprinklers must be well marked and secured with a lock and/or chain to keep them from being accidentally shut off.
A waterflow alarm
NFPA doesn’t require a home fire sprinkler system to have a waterflow alarm, but many local governments do. As you’ve likely guessed, this alarm sounds when the sprinklers are activated and water begins to flow through the system. Most of them use a plastic paddle that is inserted into the pipe; when the paddle is moved by enough water, it triggers a bell. These alarms may be connected to a centralized alarm monitoring service which will immediately dispatch firefighters to the home.
A waterflow alarm will need to be briefly tested as part of regular annual testing. If it’s connected to an alarm monitoring service, they will need to be notified prior to the test.
Backflow preventers and water meters
Some local water authorities require the use of a backflow preventer and a water meter. The backflow preventer stops stagnant water that sits in the sprinkler system from traveling back into the potable water supply, whereas water meters enable local authorities to monitor and bill separately for sprinkler system usage.
Each of these additions adds friction to the system, which ups the pressure requirements that must be accounted for in hydraulic calculations. NFPA stipulates the use of taps and meters of at least 1” to minimize this friction. A significant benefit of a multipurpose system is that it requires neither of these components since the sprinklers are integrated with the home’s circulating cold-water plumbing.
Choose the right components for the right sprinkler system
In the end, the right system for your home depends on what will work best, the expense, and any local government requirements that add complexity. Regardless of the exact system, all of them are reliable and becoming even more affordable, while continuing to save lives and property – making them a potentially invaluable investment.
If you need to buy parts for your home fire sprinklers, check out QRFS’ selection of residential system components or use the search bar at the top of the page to find what you’re looking for.
If you have any other questions about residential fire sprinklers or need help finding an item, give us a call at 888.361.6662, or fill out our contact form and we’d be happy to help.