It takes a lot to keep a water system healthy. In Union County this month, public works employees have been cleaning the water mains using an unusual procedure called “ice pigging.” We went to see how it works.
First, a little lesson about the kind of pig we’re talking about. A “pig” is a device for cleaning and inspecting pipes. Early versions squealed as they skidded through pipes – thus, the name. Usually they’re mechanical. But a few years ago, researchers in Bristol, England, developed a method for using ice to remove sediment and deposits from water pipes. Now, water systems around the world are beginning to adopt the technology.
Utility Services Group of Atlanta is the only company licensed to provide the service in the U.S., working with about 170 systems. Union County is one of the first in the Carolinas to use it, says county spokesman Brookes Versaggi:
“There’s lots of ways to flush pipes,” he says. “The way that we used to do it was with water, and it was injected with such a force that it would scour the pipe walls. And it worked well, but it used lots of lots of gallons (of water), it used thousands more than what we’re doing today. So what we’re doing with the ice slurry, it’s going to use a lot less water and (be) a lot more environmentally friendly.”
A large truck is parked in Olde Sycamore, a northern Union County neighborhood of brick houses with green lawns. It’s an ice machine on wheels, turning a mix of water and salt into a slurry called an “ice pig.”
The truck pumps it into the water main through a hose attached to a fire hydrant.
“And so here in just a moment, once they get the final readings, we will close the main line valves that will depressurize the water main to a certain extent,” explains Jonathan Smith of Union County Public Works
“And then the ice pigging company will put the ice slurry into the water main, and then we will open up a control valve, and the water itself, the flow itself will push the ice, which will in turn scour the pipe.”
It’s quieter in the cul-de-sac up the street, where water is beginning to flow from a hose in the street into another truck. There, a meter checks the salt level and clarity.
A few minutes later the ice emerges from a hose onto the street. It carries dirt and other sediment as well as mineral deposits scoured from the pipes.
The brown and white slush pours from the end of the hose and workers use shovels to push it into a nearby storm drain. When it runs clear, they’re done.
Smith says ice pigging works well.
“The ice usually doesn’t get stuck in the line, whereas mechanical pigging you do, and sometimes in mechanical pigging you have to dig out the water line. Ice pigging can make the bends that mechanical pigging cannot. And we’re seeing great results in this neighborhood from the ice pigging,” Smith says.
Every year, Union County cleans part of its 1,000 miles of water mains, and ice pigging has been used for the past four. If you don’t do it, sediment and minerals accumulate and that affects the taste, clarity and quality of your tap water.
The pipe cleaning operation wrapped up this week.