A team of researchers from the University of Hawaii at Manoa Engineering school has found that commonly used grease traps may actually do more harm than good.

When homeowners, restaurants, or anyone else dumps common household grease (think bacon fat) down their sink, a waxy fatty deposit forms on the inside of sewer lines. Over time, these so-called fatbergs accumulate more and more fatty deposits, reducing the diameter of the pipe until it clogs completely.

When that happens, the raw sewage has no place to go but backwards, either flooding into people’s basements or leaking out into the street, eventually finding its way to rivers and streams. Not to mention, it’s bad for business, as no restaurant wants to smell like a sewage treatment plant.

To avoid this worst case scenario, many restaurants install wastewater grease traps between their kitchen drains and sewer pipelines. These grease traps are designed to filter out fat, oil, and grease (FOG) before it becomes a fatberg.

Instead, the University of Hawaii engineers discovered that microorganisms that live inside these traps actually help produce long chain fatty acids that ultimately collect in sewer mains downstream.

“We are interested in the biological processes that contribute to sewer systems deteriorating and in developing engineering solutions that can improve the sustainability of sewer infrastructure and help protect public health and the environment,” explains Dr. Yan, who helped lead the study.

Most older homes have sewer lines with a 40-year lifespan; however, cured-in-place pipe (CIPP) repairs to these systems, one possible solution to the problem, can last for roughly 50 years. But these FOG deposits can cause serious sewer degradation that costs cities serious money, and officials often don’t know there’s a problem until it’s too late.

Just this week in Gwinnett County, GA, a fat deposit buildup led to 4,000 gallons of raw sewage leaking into the Yellow River.

If the study’s findings prove true, then restaurants’ grease traps could actually be aggravating a problem that’s already wreaking havoc on the nation’s plumbing infrastructure.