WASHINGTON — As the lunch hour faded on a recent workday, Ed Hairfield and his crew roared into the parking lot of a Panda Express.

They stood a few feet from the Hyattsville, Md., restaurant’s door, where mouth-watering aromas drifted out each time it opened. But the crew of one of the Washington, D.C., area’s largest sanitary systems could not care less about the menu’s SweetFire Chicken Breast. They only cared about the lard.

Every day, up to five times a day, Hairfield’s six-man Washington Suburban Sanitation Commission crew pops open a hatch next to a store or restaurant to study a nasty sight: lumpy grease buildup from cooked animal and vegetable fat.

It’s the same stuff that clogs arteries and stops hearts, and the crews are deployed to keep it from doing the same to WSSC’s network of sewer pipes. This year and last, inspectors issued 31 citations to establishments for failing to properly maintain pricey interceptors that stop thick kitchen grease from backing up pipes.

But the blame doesn’t fall solely on restaurants. Grease is poured down kitchen drains by hundreds of thousands of household cooks in the region, and by hundreds of millions of people nationwide. Coagulated fat from fried bacon and potatoes cools into a pipe-choking yellowish blob after flowing into sewers, causing serious overflows that threaten homes.

Grease plays a starring role amid the other junk, Hairfield said. “When you put grease on top of onion skins, potato skins and all that other stuff, it’s like glue. It sticks to the pipes.”

The presence of fat in the bowels of cities and suburbs is just one symptom of a more pressing problem in the nation’s old and decrepit sewers, said Adam Krantz, managing director of governmental affairs for the National Association of Clean Water Agencies.

“We are facing a looming crisis in terms of our water infrastructure,” Krantz said. “We are nearing the 40th anniversary of the Clean Water Act in October, and we are seeing some pipes and treatment systems nearing the end of their useful lives.”

Money used by utilities to upgrade facilities and cut down on overflows to meet Environmental Protection Agency regulations could buy larger and more efficient pipes that can overcome grease, tree roots and other problems.

But the estimated pricetag for fixing the nation’s new water infrastructure over the next 20 years is steep — $334 billion, according to the EPA. So cash-strapped utilities are making do with what they have.

“If we could reduce one tablespoon of grease per household, that’s 57,000 gallons of grease we wouldn’t have to deal with,” said George Martin, general manager of a sewer system in Greenwood, S.C.