Web edition: October 22, 2008
Public utilities spend a fortune each year cleaning water and supplying it to distribution lines that feed our faucets. Much of that water, however, is lost en route. Corrosion is rusting through water mains, opening holes that allow, on average, some 15 percent of the starting flow to disappear into the ground, notes Marc Edwards, an environmental engineer at Virginia Tech, in Blacksburg. The estimated cost of those losses: $3 billion annually.
But financial waste is not the leaks’ only cost, Edwards observes. He described a host of water concerns to a handful of attendees from the Society of Environmental Journalists annual meeting who toured his lab last Saturday.
One particularly nasty ancillary cost: germs that enter water mains through holes eaten out by rust.
Edwards points out that water mains are often laid underground near sewer pipes, which also corrode and leak. Fecal germs can migrate from sewage leaks toward a water main. Admittedly, when water is squirting out under pressure from holes in those mains, bugs can’t enter. However, Edwards told me, mains occasionally experience significant drops in water pressure. When that happens, instead of water squirting out of the pipe, water will momentarily get sucked in from the anything-but-sterile environment outside it. When pressure in the main picks up again, it propels the now potentially tainted water toward our homes. Yuck.
Think he’s exaggerating to grab a reporter’s attention? Uh, no.
Modeling data indicate that 13 to 31 percent of pipe-intersection joints are at substantial risk for germ intrusion, such as when pressure drops occur during pumping transients, water-main breaks, or repairs. The source for these stats: a 2001 report by Gregory J. Kirmeyer of the Omaha, Neb.-based HDR Engineering and Mark W. LeChevallier of the utility American Water, in Voorhees, N.J.
And it gets better. Kirmeyer and LeChevallier reported results of monitoring tests. These “confirmed that waterborne pathogens are very common in the environment external to water distribution mains.” Those germs were identified “in undisturbed soil and water samples immediately adjacent to distribution system pipelines,” they said.
Okay, a germ here or there isn’t likely to make most of us sick. Our bodies have a tremendous capacity to fight infection. But homeowners can do things that can inadvertently — and quite dramatically — spur the growth of any incoming germs, Edwards says. Such as by turning down the temperature on a home’s hot water heater.
For more on that, see tomorrow’s blog.
Kunkel, G., K. Laven and B. Mergelas. 2008. Does Your City Have High-Risk Pipes? Journal of the American Water Works Association 100(April):70.
Kirmeyer, G.J. and M.W. LeChevallier. 2001. Pathogen Intrusion Into Distribution Systems [Project #436]. American Water Works Association Research Foundation.