Although residential sprinkler systems have proved to be the most effective form of life and property safety available, annual reports from the National Fire Protection Association show that only 2% of all homes are protected with sprinklers. A new method of installing sprinklers promises to change that.

Multipurpose sprinkler/plumbing systems are now available for private homes in the United States, Canada and the United Kingdom, and they're also being introduced in European nations. The systems have technical, economic and marketing advantages over stand-alone systems, which include overcoming the two biggest barriers to the advance of residential sprinklers: cost and builder resistance.

With these advances, fire chiefs will find it easier to promote residential sprinklers, either with sprinkler ordinances or as optional upgrades for new homes.

Multipurpose systems defined

When the piping for a residential sprinkler system also serves as the plumbing pipe, it's defined as a multipurpose system. The use of one set of pipes for both purposes reduces cost and eliminates the need for cross-connection devices, which are required to prevent contamination of the potable water supply.

The stagnant water in stand-alone sprinkler systems is considered a potential health threat, and public health officials require that they be separated from potable water by check valves or backflow preventers. The type of multipurpose system shown in Figure 1, at right, eliminates stagnant water. The deletion of a check valve or backflow preventer can reduce installation costs from $50-$500.

Multipurpose systems use UL-listed pipe and fittings. They have been in NFPA 13D since the early ’90s, but they didn't gain notice until the 1999 edition. Two key revisions to that edition have increased interest in this method of fire protection. The first revision reduced the minimum working pressure of pipe from 175psi to 130psi. The original pressure requirement had been imported into the original edition of NFPA 13D from NFPA 13, with the justification that sprinkler pipe had to withstand the higher pressures generated through fire department connections.

To push through the revision, supporters of multipurpose systems pointed out that NFPA 13D doesn't require fire department connections. Since the pipe would never experience more than normal plumbing pressures, reducing the working pressure was justified. Plumbers routinely install pressure-reducing valves when the water supply pressure exceeds 70-80psi, so the 130psi requirement is well beyond the expected normal operating pressure.

The other revision reduced the minimum pipe diameter from I-inch to H-inch, the diameter normally used for plumbing systems. NFPA 13D requires the system to supply enough water to flow the two most demanding sprinklers. Supporters of the change documented that the smaller diameter could supply the required amount of water by creating a compound loop system.

The NFPA 13D technical committee accepted the change with additional criteria. It required that the H-inch multipurpose system have a minimum of three paths, which the hydraulic efficiency of the compound loop accomplishes.

Once the water leaves the water supply manifold, it's divided into multiple paths. The water from the multiple paths is recombined at the multiport fitting of the flowing sprinkler. The H-inch system uses a multiport fitting that can receive water from four paths. Where a sprinkler fitting is near a plumbing fixture, one of the four ports is used to feed the fixture. The remaining three ports supply water to the sprinkler.

The sprinkler family tree

Supplying water to sprinklers from more than one path has been used for generations. There are three basic layouts for sprinkler systems. The original systems were designed in a “tree” layout that supplied water through a cross main, which acts like the trunk of a tree. (See Figure 2, page 46.) Sprinklers are located on branch lines attached to the cross main, and the arrangement resembles a tree.

The second layout is the “simple loop” system, where a second cross main is added. (See Figure 3, page 46.) The extra cross main splits the water supply into two paths to a flowing sprinkler. The increased hydraulic efficiency allows the use of smaller-diameter cross mains and branch lines.

The third layout is used to increase hydraulic efficiency even more. It's the gridded layout, where additional cross mains are used to form the grid pattern. (See Figure 4.) All of the pipe sections are interconnected, so water flows through each. The specific path depends on the location of the flowing sprinkler. Compared to a simple loop system, the multiple paths compound the number of loops, and thus the name compound loop system.

The H-inch multipurpose system is a form of a gridded system. (See Figure 5.) The only difference is that the multipurpose system uses flexible nonmetallic pipe that attaches to the multiport fitting at angles. Thus the pipe sections travel in arcs instead of right angles like rigid pipe.

Unlike tree or simple loop systems, water flows through every pipe section and sprinkler fitting in a multipurpose system each time a plumbing fixture is opened. This offers two technical advantages:

1. The volume of water flowing in each pipe section is relatively small and has a corresponding low velocity. This allows the system to supply the required volume of water to sprinklers with a lower supply pressure.
2. The sprinkler system is constantly tested. Every time someone opens a plumbing fixture, water flows through the entire system. If the plumbing is working, so is the sprinkler system.

The marketing advantage

Two economic advantages of these systems have already been noted: one pipe system instead of two, and elimination of check valves or backflow preventers. Home builders note another key advantage: the ability of one subcontractor to do the work of two. This increases their efficiency and ultimately reduces construction costs.

Perhaps the biggest advantage of multipurpose systems is their marketing potential. People are largely unfamiliar with fire sprinklers, and marketing gurus will tell you that sales resistance and negative images are highest when consumers are faced with an unfamiliar product. We've all heard the fears expressed about sprinklers over accidental discharge and “ugly” sprinkler heads protruding everywhere. These are normal consumer reactions to something that's foreign to them.

The experience to date with multipurpose systems indicates a huge change in perception among home builders and buyers. The reason is simply that people are very familiar with plumbing systems, so sales resistance and negative perceptions are low. Marketing sprinklers as a fire-safety addition to the plumbing takes advantage of their familiarity with — and trust in — domestic plumbing.

Can multipurpose be monitored?

This is a frequently asked question, because sprinkler flow switches operate when water flows, and water flows through multipurpose systems every time that a plumbing fixture opens. A flow switch can be installed by adding a flow-sensing valve that distinguishes between plumbing fixture flows and a sprinkler flow.

To add a flow switch, the installer places it downstream from the flow-sensing valve on the water supply pipe. The valve is set to be closed when low pressure losses indicate plumbing fixtures are operating. All of the water to the system flows around the valve and flow switch. When a sprinkler opens, the larger pressure drop will cause the valve to open. The water then flows through the sprinkler flow switch and activates the alarm.

Water softeners are a special case, as they can have low outputs, sometimes as low as 10gpm. Sprinkler systems require a higher flow, so the bypass also ensures adequate water to the sprinkler system when a water softener is installed. The flow sensing valve directs the water through the water softener until it senses a large pressure drop in the system, indicating that a sprinkler has opened. It then opens, and all of the water flows through the open valve directly to the system.

Laying the groundwork

Fire officials who want to introduce multipurpose systems need to address two issues. First, they need to confirm that their jurisdiction accepts nonmetallic plumbing and sprinkler pipe. Some areas haven't adopted the latest plumbing codes and may still restrict the pipe to metallic materials. Resolving the problem might be just a matter of pushing for adoption of current plumbing codes.

The other need is to assure that qualified contractors are available. Training is not an issue because classes are easily arranged. For example, the manufacturer of the H-inch system factory-trains its contractors. The challenge is licensing. Multipurpose systems combine fire sprinklers with plumbing systems, but the contractor licensing laws in many states are based on the traditional approach: separate systems, separate occupations to install them. Where that's the case, the regulations need to be updated to include a new category of contractor who can install fire sprinklers on potable water systems.

The Residential Fire Safety Institute has compiled a list of state licensing regulations that can help jurisdictions determine the steps to take to create a new license category. The list shows a wide variety of regulations throughout the United States, but also shows some states that have already developed reasonable requirements for multipurpose system installers.

Florida regulations are a good example. The state licenses sprinkler contractors and plumbers. Instead of a blanket regulation that covers all sprinkler contractors, a contractor who installs multipurpose systems can apply for a 13D license. There are no experience or training requirements for things like high-rack storage, standpipes or fire pumps. Since potable water is involved, the multipurpose contractor must also have a plumbing license. Getting a 13D sprinkler license is then a matter of attending an approved class on 13D systems and taking an exam based on that standard.

Unfortunately, one-size-fits-all contractor licensing laws pose a problem. Sprinkler contractors aren't rushing to embrace changes that will increase competition. Some firmly believe that sprinkler systems are complex enough that the contractor should be fully qualified to perform any sprinkler work, from homes to high-rises. They will often ask, “Who will design the system?”

Multipurpose systems still need a qualified person do the designs. The traditional approach has been to require that the contractor have an employee with the proper background. The sprinkler industry has relied on certification from the National Institute for Certification of Engineering Technologies for demonstrating the qualifications to design systems, but the process requires years of work experience in the sprinkler industry, something that plumbers won't have. It also requires practical experience with designing commercial systems, something that a multipurpose system designer will never do.

The H-inch multipurpose system is factory-engineered and -designed, so contractors don't need employees with design credentials. The factory provides the necessary training that qualifies the contractor to install the sprinkler components. This can make it easier to adopt state licensing laws that will allow contractors to install 13D systems without requiring the level of expertise needed for commercial sprinkler work.

When residential fire sprinklers were introduced in the early 1980s, they held a lot of promise. But issues like builder opposition, lack of consumer awareness, installation costs and lack of installers have kept them from meeting our expectations. The multipurpose systems now available are removing all of those barriers. Are you ready to take home fire safety to the next plateau?

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Patrick Coughlin is the manager of fire sprinkler codes and standards for the Wirsbo Company. He served as the director of Operation Life Safety, a public/private partnership of the USFA, IAFC and private industry whose mission is to reduce residential fire deaths and injuries by installing fire sprinklers and smoke alarms and teaching fire-safe behavior. A graduate of the National Fire Academy's Executive Fire Officer Program, Coughlin has a bachelor's degree in sociology from Purdue University and a master's degree in sociology and public administration from the University of Minnesota.

For further information

For additional information on residential sprinkler systems, contact the following organizations:

• National Fire Protection Association, “U.S. Experience With Sprinklers: Who Has Them, How Well do They Work,” produced annually. NFPA, 1 Batterymarch Park, Quincy, Mass. 02269.
• Residential Fire Safety Institute, 763-416-0527, or e-mail Dana Bies at <rfsimgr@mn.mediaone.net>.