Those who oppose the mandate say they’re concerned about the potential of pipes freezing in colder climates, damage from accidental discharge of sprinkler heads, and the availability of adequate water supply in homes served by well water. Let’s take a look at those arguments…
 
Frozen pipes?
I think most of this concern relates to a standalone system, which is a system of piping separate from the home’s plumbing. The water in these pipes is stagnant until a sprinkler head activates. Stagnant water is more susceptible to freezing than moving water (backflow valves are required to prevent contaminating the water supply), but what are the chances of water freezing in a heated home that is properly insulated? And don’t we take precautions in new construction to protect all piping from freezing? Obviously, all pipes containing water need to be installed on the warm side of the insulation!  An alternative to the standalone system is multipurpose systems; the piping in these systems is part of the home’s cold-water line, often made of PEX (which is less susceptible to freeze damage), and the water’s always moving.  Concern about frozen pipes is a pretty lame argument.
 
Accidental discharge?
Sprinkler heads are activated by very high heat, like the kind that isn’t likely unless there are flames present (155°F-175°F, depending on the type of head). So only the head(s) closest to the flames actually discharge water. Research shows that chances of an accidental discharge due to a defect in the sprinkler head are 1 in 16,000,000.
 
Well water?
The NFPA 13D (the National Fire Protection Association’s residential-sprinkler code) requires enough water for two sprinkler heads (which use about 26 gpm combined) to discharge for 10 minutes (for homes over 2000 sq. ft.; it’s 7 minutes for smaller homes). Achieving that volume can be accomplished by a pressure tank(s), a bladder tank(s), a storage tank(s), a cistern, a well equipped to draw that amount—or a combination of these.
 
It’s got to be the cost!
Most people—including those opposed to the code—get wound up about the cost. Money’s tight all around these days, so any increase in construction cost is certainly a concern here. But the cost is much less than you probably think. Costs can range quite a bit around the country, from 87¢ to $4 per sq. ft. (materials and installation). The average is about $1.50 per sq. ft., which typically comes out to about 1% to 2% of total construction cost for modest homes and much less for upper end homes. Our experience has been that it is about $2.00 per sq. ft. locally and less than 1% of the total cost of our homes.  So, for our clients, having a fire sprinkler installed in a nicely finished 3,000-sq.-ft. home will cost about $6,000. That’s pretty cheap insurance in my opinion for a $900,000 home.  Think of what it would cost to repair the smoke and water damage from even a minor fire that was put out using the fire department; more than $6,000 I would wager!  And speaking of insurance, I would think that you would get a pretty nice discount from your homeowner’s insurance for having a home protected by a fire sprinkler system.
 
Now, consider that fire sprinklers and smoke alarms combined reduce the risk of death by 82%. And in the 20 years that Scottsdale, Ariz., has had fire sprinklers on the books, no one has died from a fire in a home equipped with sprinklers.
 
Is it worth the extra expense?  What do you think?