Before a fire sprinkler system in a house can help protect its occupants from a fire, it has to survive at least two difficult obstacles. First, it has to be tough enough to last through possible neglect from its owners. Second, it must be able to handle the cold stuff that Mother Nature can throw at it. This article will discuss how a home fire sprinkler system can need only minimal maintenance and survive the nasty winter surprises through proper design and material choice.

One thing a house has to endure is its occupants. Homeowners do not always follow through on things that need to be done. “Change your air filter on your HVAC system”; “change your batteries in your smoke alarms”; ”clean you rain gutters”, and countless other reminders are continually bombarding us. Why, because many of us will NOT DO THEM if left on our own. Some maintenance must be done to live in a safe home. However, reducing required maintenance should be a primary objective.

Other fire sprinkler codes (NFPA13 – commercial buildings and NFPA 13R- for apartments and condos) both require at least one professional inspection every year and require a 24/7 electronic alarm that ensures valves are not being tampered with and a number of other items. These systems are designed with an understanding that they will be regularly maintained by trained professionals.

This is NOT the case with home fire sprinklers. None of these frills are involved with a 13D system (NFPA 13D is the standard for fire sprinklers used in single and two family homes). It will only get the maintenance that the homeowner is willing to give it. This is where purposeful design comes into play.

The 13D code goes a long way in helping a designer make an almost maintenance free automatic fire sprinkler system. It requires only the standard operating water pressure of the domestic (regular household) plumbing system. This is a huge factor in simplifying the design. Other sprinkler codes (NFPA13 – commercial and NFPA 13R- for apartments and condos) require that they have a fire department connection installed. This means that a fire truck can pull up near the building and hook up a hose to the structure’s sprinkler system to pressurize it with the pump on the fire truck. While this effectively increases the efficiency of the sprinkler system by increasing the water pressure, it requires the sprinkler system to be piped out of material that can withstand water pressure at least twice what the normal plumbing system in your house would need. Necessary standards like this reduce the material options for the designer in 13 and 13R systems. Because of its light weight and ability to handle the pressure and heat, CPVC plastic has worked well, especially in 13R systems, and has become the standard.

A 13D fire sprinkler system only has to operate at normal house water pressure. No fire department connection is needed. This has opened the door for a “multipurpose” system with the domestic water (unheard of in 13 or 13R systems). A multipurpose system (sometimes called “flow-through”) allows the sprinkler and the domestic plumbing to use the same water. For the first time, a fire sprinkler system does not have to have a dedicated water supply. A multipurpose system also means that an anti-backflow prevention device is not needed since the water in the sprinkler system is not stagnate as in a “stand alone” system. The water in a multipurpose system is potable since it is an extension of the domestic plumbing. [Usually, the water closets (toilets) are fed by the water in the sprinkler system. When a toilet is flushed, fresh water flows through the sprinkler system.] Having no anti-backflow device means there is one less part to fail in the future and one less item to be maintained.

Also, when using the 13D multipurpose design, as long as the pipe is rated for use in fire systems, a designer is permitted to use other types of piping materials. One of the newer choices of pipe is crossed-linked polyethylene or “PEX” pipe. This is the pipe used by many plumbers across the country in new houses for hot and cold water. This material works well for multipurpose fire sprinklers. This multipurpose design and material choice keeps the maintenance cost very low and keeps the quality of the system very high.

The range of needed maintenance for a home fire sprinkler system can widely vary depending on the systems design. For instance, a multipurpose fire sprinkler system can be almost maintenance free (visually check for leaks and turn on a test valve for about a minute each year) with no cost to the homeowner. On the other end of the scale is a “stand alone” (traditional, dedicated water supply) system with an anti-backflow device that is charged with anti-freeze. This type of system will need some maintenance every year by professionals. This will include inspection of the anti-backflow device and checking the strength of the anti-freeze and recharging as needed. This can run as little as fifty to as much as hundreds of dollars per year, depending on how much anti-freeze solution you need. The “stand alone” systems are designed similar in some ways to the 13R systems and they reflect this by requiring some of the same regular maintenance. Keep in mind that maintenance is not a negative thing in commercial or high density residential structures; it is by design, to keep them running smoothly and is required by code. But 13D has no such enforceable requirements and does not need those heavy maintenance codes if we keep it simple by design.

This being said there are places where a higher maintenance, antifreeze filled system is the best choice (like a vacation home that will not be occupied in winter and will have the potable water turned off and drained to winterize the house), but they should be rare. The standard fire sprinkler design should be safe and efficient, yet simple and needing the lowest possible upkeep with the fewest parts to fail. This is going to require the sprinkler contractor to help educate fire authorities and inspectors. Many fire authorities have only seen 13 and 13R systems and have yet to learn how multipurpose systems are designed. This effort will benefit all concerned, especially the homeowner.

The house goes through other problems in its life too, like energy outages and severe weather. Let’s face it, our climate, no matter where we live, seems to throw us some interesting curve balls and the future forecasts are more of the same. The likelihood for a house to have sustained energy outage with severe cold weather is higher than the chance of fire during its lifetime in most neighborhoods.

Remember, under normal usage, within a heated house and properly insulated piping, both CPVC and PEX pipe will give fine service for many years. Think of the regular plumbing in the house…under normal usage, no anti-freeze is needed and the pipes do not break. The multipurpose system is an extension of that regular plumbing system. But, what about the not-so-normal times? What about the combination of cold weather and no power? What happens to the sprinkler system then?

As an example of what can happen, let’s look at the weather in the State on Kentucky in January of 2009, just last month. While it is common for the area to dip below freezing in the winter, nobody expected to see an ice storm come through and lay three inches of ice over a substantial part of the state. With that much ice, massive power failures occur. So now you have cold temperatures for an unexpected duration and no power to many homes. In just two to three days the interior of many homes is below freezing and there is very little the average homeowner can do to stop it. For the plumbing in these houses, insulation is turning into a moot point as the cold has fully penetrated. It should be noted that a home fire sprinkler system in this frozen condition will not fight fires…it will have to thaw out first…but it should not be doomed to bursting and flooding the house. That is just poor design and material choice.

These pictures were taken in Washington State during January 2009. The house was only 6 months old and had a furnace failure. The home went without heat for about four days, causing the water inside the fire sprinkler piping to freeze and break the CPVC material. In contrast, the domestic plumbing in this house was installed with PEX piping and did not have any freeze breaks.

Unfortunately many installers of home fire sprinklers cling to the 13R model of sprinkler systems and want to construct it out of CPVC, which is accepted by the code. However, CPVC does not handle freezing water inside it very well…it shatters. If the same home has a multipurpose system piped with PEX tubing, it has a much better chance of survival.

PEX, by its nature, will expand when frozen, and then return to its normal size when thawed, without breaking. Yes, it is possible to freeze and break PEX pipe, but it has a MUCH higher chance of making it through a freeze than CPVC. This is one of the reasons that in thousands of homes, plumbers have made the switch to PEX for their domestic water service installations in the past decade. It is also the most common choice for in floor hydronic heat. Many plumbers agree that they have MUCH less in-wall freeze breaks with PEX than with copper or CPVC.

You can see that design and material choices in the home fire sprinkler system will be making a difference here. It is about increasing the survival odds of the fire sprinkler system. Under these circumstances the choice of CPVC piping and either no antifreeze or not enough antifreeze in closed systems have doomed the fire sprinkler system to catastrophic failure. The attics in the homes in this scenario will have shattered piping waiting to thaw and then flood their attics, creating a nightmare for the homeowners to try and fix.

While a CPVC system with a large amount of antifreeze is the time tested method for a sprinkler system to have a chance of being functional during such a situation, it also generates the maximum maintenance expense to the homeowner, assuming the homeowner will stay faithful to the larger maintenance schedule (antifreeze breaks down with age and must be replaced to be effective).

Maybe some innovation is in order, to come up with other ways to prevent a system from freezing, with low to no maintenance. Even when efforts to keep it from freezing fail, the material choices made should maximize cold weather survivability. There must be a balance found between cost of long-term maintenance issues and the strength and stability of the fire sprinkler system to withstand things like power outages and surprise cold weather.

We need to design the home fire sprinkler system to survive the unexpected cold and require minimal maintenance, so it can be there to fight potential fires for decades to come.

Michael Cox serves as sales and marketing manager for 13dPEX.com, a design and distribution company in Bellingham Washington, dedicated to NFPA 13d sprinkler systems. This firm supplies design, tools, pumps, and installation materials to plumbers and others who are contracting to install 13d systems. Specializing in multipurpose or flow through design using PEX tubing as a primary material. He has worked in life-safety and fire prevention for more than two decades, holds a Washington State certificate for sprinkler design, and has worked with AHJs and Fire Chiefs through out the state. He is currently teaching a seminar program designed to prep plumbers and others to get their state certification.