Overhead sprinkler systems have protected public buildings from fire for more than a century. About 20 years ago a simpler, sleeker, less expensive counterpart of the clunky commercial systems became available for private houses as well.
But somehow the word hasn’t gotten out, going by a recent survey of consumers by the National Fire Protection Association (nfpa.org). It found that although 92 percent of those surveyed thought sprinklers were effective in fighting fires, 48 percent had no idea there was a residential version.
Currently, less than 1 percent of new houses have a fire-suppressing sprinkler system built in, although the NFPA says they reduce the chance of dying in a fire (and property loss) by one-half to two-thirds.
How sprinkler systems work
The idea is logical and simple. Instead of waiting for the fire department with its high-volume hoses, fight the fire automatically as soon as it starts with water that’s already there.
The system distributes your household water supply to rooms through a separate network of concealed plastic pipes. The sprinkler heads are flush-mounted and cosmetically capped to blend in so your house doesn’t look like a factory.
The sprinkler system has the same pressure as your tap water, but the supply is stopped at each sprinkler head by a temperature-sensitive plug. It releases water at about 160 degrees.
Sprinklers aren’t triggered by smoke–a common misconception. Another is the idea that when one head is triggered, every other head in the system starts spraying. A building-wide deluge makes for funny scenes in movies, but that’s not the way it works.
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If a fire spreads, adjacent heads will only release water as their plugs give way in the heat. But multihead releases are unusual, according to the Home Fire Sprinkler Coalition (homefiresprinkler.org). It says that almost all fires are contained by the operation of just one sprinkler head.
Many people also think sprinkler systems may flood the house and create more damage than the directed sprays of fire hoses. Actually, it’s the other way around.
A residential fire sprinkler uses an average of 341 gallons of water to control a fire. Firefighters, on average, use 2,935 gallons–in large part because the fire is larger by the time they arrive.
Manufacturers say reduced water damage is a major source of savings with sprinkler systems–in addition to a reduction in your home insurance costs. In a typical scenario, the fire department will check the building even if the sprinkler has extinguished the blaze. Then the sprinkler water supply is turned off until you have the activated sprinkler head replaced.
Cost and effectiveness
Those unusually precise water-use statistics come from the best of all proving grounds for sprinkler systems, Scottsdale, Ariz. The city has been an ideal source of practical information since 1986 when an ordinance went into effect requiring sprinklers in all new residential construction.
The NFPA says that more than 50 percent of the homes in Scottsdale (more than 40,000) are now protected with sprinkler systems. It makes for a huge database–and a strong case for sprinklers.
– Data collected by the city fire department indicates that the systems have saved 13 lives and prevented more than $20 million in property loss.
– Initially (from 1985 to 1992), the average property loss from fire in homes with sprinklers was $2,665, and $17,067 in homes without them. During the last three years, average fire loss in the homes with sprinklers was $2,166, compared to $45,019 in homes without them.
– More than 90 percent of home fires in Scottsdale with sprinkler systems were contained with the activation of one sprinkler head.
When it comes to price, most sprinkler groups say contractor-installed systems run just over 1 percent of the cost of construction, or approximately $1 to $2 per square foot of living space. Retrofits in existing homes are more, about $2 to $3 a square foot.
In Scottsdale, typical installed costs are about half the national average–a result of competition among many installers in a market where installations are required.
But actual cost depends not only on the size of the house, but also on its layout, framing system and whether the sprinklers are tied into an alarm system. Most installations have a flow switch that can activate a stand-alone audio or visual alarm. But sprinklers can also be tied into a central security system.
Fire safety groups such as the NFPA, which recommends the systems, remind consumers that sprinklers should be used in addition to, not instead of, smoke detectors.