Reverse flow is the problem. In a serious house fire, for example, firefighters could draw so much water out of the water main that stagnant water in residential wells or sprinkler and irrigation systems might be sucked into the public main. Enter the backflow preventer, a pipe with one or more check valves that prevent flow reversal.
But do the preventers with their prominent pipes and valves need to stand out so in the natural landscape, the Woodside Town Council wanted to know. The council at its Jan. 25 meeting discussed a zoning code amendment to allow them in setbacks. Representatives from the California Water Service Corp. and the Woodside Fire Prevention District attended.
"There are some ugly ones in the town," Denise Enea, fire marshal for the district, admitted.
Because they have such a vital role, the law requires that preventers be above ground, near the road and inspected annually. Proximity to the road allows the public to see leaks and call the water company, said Tony Carrasco, manager of Cal Water's Bear Gulch district, which provides drinking water to Woodside, Portola Valley, Atherton and Menlo Park.
Cal Water prefers that the devices be as close to the main as possible, which means at or near the property line, Mr. Carrasco said. The preventers can be moved further in but only if the buried water line connecting to the main is made inaccessible with a thick jacket of concrete or a sturdy metal or PVC sleeve.
Such protection discourages ambitious plumbers looking for a place, any place, to tap in — a nagging problem, apparently. "Maybe that would deter them," Mr. Carrasco said in an aside. "Maybe they would communicate with the homeowner a little bit more."
Roads with a view
Opinions differed as to the impression made by backflow preventers from the perspective of a passing vehicle.
"These things are not that big," said Councilman Dave Tanner, a builder.
"They are. They're huge," said Councilman Peter Mason, an architect.
Ninety percent of Woodside homes use water lines of 2 inch diameter or less, said Cal Water Assistant District Manager Paul Molder, but there are estates that need larger pipes. Shielding options include landscaping, fabric jackets and fake rocks.
In considering the appropriate setback, the council discussed linking the maximum distance from the road to the size of the water line. Pipes of up to 2 inches in diameter could have up to 10 feet, while larger ones could be allowed 25 feet to 30 feet.
"The key thing here is we don't want them right on the road," Councilman Dave Burow said.
Which houses will require one? Cal Water tends to want them on sites that can expose water to contaminants. Examples include an unapproved well or any container in which water can become stagnant, including swimming pools and fire sprinkler and irrigation systems, Mr. Carrasco said.
"Nothing from the (state) Department of Health indicates that every property will need one," he told the council. "If we see somebody that has a well and no device, we will contact them and work with them and educate them."