Frigid temperatures can cause smaller pipes to freeze and break this time of year, but that’s not usually how they trigger larger water main breaks like many of the dozens that have Baltimore public works officials on alert this week.
Those are more likely to be a consequence of geology, and geography, public works officials say.
The ground may seem stable, but it’s always moving, shifting objects buried within it, explained Kurt Kocher, a city spokesman. When frigid temperatures come and go, the freezing and thawing makes that movement more severe.
“Things are going to move and shift,” he said. “It’s a real shock.”
The effect is strongest in areas with softer, more porous ground — such as the parts of the region at the edge of the coastal plain, an area of sand and clay that extends from the middle of Baltimore across the Chesapeake Bay and the Eastern Shore toward the ocean. A boundary known as the fall line, dividing the rocky uplands of the Piedmont Plateau from the coastal plain, bisects the city.
That makes areas across East and Southeast Baltimore more prone to main breaks, Kocher said.
The age of Baltimore’s plumbing — much of it was installed more than a century ago — can also be a factor, he said. Corrosion weakens pipes, and extra movement and stress from cold temperatures can then break them.
“The longer a pipe’s in the ground, the more it moves,” he said.
Narrower conduits like the lateral lines that connect homes to the city water system are the ones residents and public works crews have to worry about freezing, if they contain standing water. That’s why officials are recommending that residents leave faucets on a trickle if pipes are exposed to the cold.
If city residents see signs of a possible water main break, they are asked to call 311; Baltimore County residents should call (410) 396-5352.