Sweeney spends his days purging sediment and slime from tap systems that deliver your favorite suds from keg to mug. His efforts help keep that gunk from ending up in your growler or glass.

It’s a process most folks probably never think about when they order a frosty cold one at the end of the day. But calcified crud and other muck that builds up in those tubular lines and taps can render a premium beverage flat, sour, headless or worse.

“It’s all about protecting the integrity of the beer,” said Sweeney, who runs Charleston-based Southeastern Tap Technicians .

South Carolina has no specific law requiring bars, restaurants and retail establishments to clean their draft lines, and it’s up to distributors to decide whether to offer the service to their customers. Some do; some don’t.

Some businesses are particular about the condition of their lines. Others, well, let’s just say it doesn’t seem to be a top priority. Sweeney has a couple of photos from some rather crusty lines he has encountered. He won’t name names, but the pictures can be accurately summed up in one word: Yeeccccchhhhh!

One memorable photo shows a thumb-size hunk of dark matter that would definitely be a buzz-kill if it plopped into in your glass.

“It had been sitting in the line for God knows how long,” Sweeney said. “I thought it was going to break my pump.”

Rich Carley, co-owner of Charleston Beer Exchange, cringes when he sees such examples of poor tapsmanship. With an ever-rotating selection of draft brews for sale, his peninsular store gets its nine lines flushed by Sweeney every two weeks.

“It’s as important as the beer itself,” Carley said. “Great beer through dirty lines is a disaster.”

Officials from the Boulder, Co.-based Brewers Association have been preaching that message around the country and handing out copies of a 58-page guide for maintaining draft-beer quality. Association Director Paul Gatza said laws vary from state to state, with some places requiring biweekly cleaning of draft systems and others requiring no cleaning at all. He argues that it makes good business sense to keep the lines pristine, regardless of the law.

“When someone feels a beer is bad, more likely, it is the draught line that needs attention,” Gatza said in an email. “An establishment that does it right retains more customers.”

That was the premise that Sweeney, a former bartender, embraced when he opened up shop a few years ago. South Carolina had just legalized the sale of higher-alcohol brews, flooding the state with myriad craft beers carrying big, bold flavors. Sweeney saw an opportunity to carve out a niche as a guardian of good tastes.

He took some classes, bought some equipment and jumped in. With a portable pump and a trunk full of cleaning supplies, Sweeney now travels the Lowcountry as a sort of roving beer rooter, cleaning lines so that specialty beers keep tasting special. He disassembles the taps, scours their parts and then blasts a cleaning solution and water through the lines.

Threats, after all, come in a variety of forms, from bacteria and mold to yeast deposits and “beer stones,” calcified chunks that can build up and flake off inside the tubing. These intruders can mess with the aroma, appearance and taste of their host beverage, reducing a pint of hoppy goodness to sour swill if left unchecked.

Brandon Plyler, manager of the Beer Exchange, said pouring from grimy lines is like going to a restaurant and eating off dirty plates. “At best, it can make a beer look muddy. At worst, it can make the beer undrinkable.”

Aaron Lucas, beverage director for Closed for Business and Monza restaurants in Charleston, said frequent cleaning also prevents one beer’s flavors from leaching into another when a new keg is tapped. No one wants to order a light lager and end up tasting the fruity flavors of a framboise lingering in the line, he said.

State health inspectors will swab taps on periodic visits to restaurants and recommend cleaning if needed, but it’s really up to establishments to police themselves to ensure a quality pour, Lucas said. Closed for Business has Sweeney clean its 42 lines every two weeks with that in mind, he said.

“Even on lighter-style beers, you’ll build up things in beer lines that can instantly trash a beer,” he said. “Craft beer is finally getting somewhere in Charleston. So you don’t want a customer to come in, taste a beer and say ‘That is terrible’ and then realize it’s because of a lack of cleaning.”