It’s 6:15 a.m. on a Sunday, and more than a dozen parents are arrayed in the lobby of Alexandria’s Lee District Recreation Center, silently reading newspapers, paying bills and doing some Christmas shopping online. A few others wander in around 9 a.m., bleary-eyed and rumpled, after alarm clocks rouse them from naps in their cars outside.

To thousands of parents throughout the Washington area, it’s a familiar ritual weekends and weekdays alike: rising in darkness, battling traffic and devising ways to productively spend time while their children swim lap after lap after lap.

Though not what might be expected of a congested metropolis prone to snowpocalypses and sweltering humidity, Washington has become a swimming hotbed known not only for producing Olympic gold medalists Mark Henderson, Tom Dolan, Mike Barrowman, Ed Moses and Katie Ledecky but also for churning out a steady stream of scholarship athletes from a pipeline brimming with talent.

Multiple factors account for the phenomenon.

The first dates back more than 50 years, says Riley Eaton, general chairman of the board of directors of Potomac Valley Swimming and a former coach with the Rockville-Montgomery Swim Club, pointing to the development of suburban subdivisions, nearly all of which boasted a community pool and tennis courts.

Summer swim leagues formed to provide basic instruction couched in fun and games, and now there are more than 30,000 summer-league swimmers in the area. And the subset of youngsters who wanted to stick with the sport once school started fueled a demand for year-round teams.

Today, those clubs — Rockville-Montgomery and Nation’s Capital Swim Club (NCAP) in particular — dominate competition in Northern Virginia, the District and Montgomery and Prince George’s counties, which is governed by Potomac Valley Swimming.

(NCAP changed its name from Curl-Burke Swim Club in September after allegations of a sexual relationship with a swimmer were made against the club’s former owner, head coach and namesake, Rick Curl.)

Despite having the smallest geographical footprint among the 59 competitive regions designated by USA Swimming, the sport’s national governing body, Potomac Valley has the fourth-most participants in the country, Eaton says, with 10,500 swimmers, and Rockville-Montgomery and NCAP boast numerous national and junior national titles.

And it’s growing at a rate that’s straining the capacity of the area’s public and private pools.

“There aren’t many new pools being built,” says Tom Ugast, chief executive of NCAP. “And that’s the struggle we’re going to have: We have nearly 11,000 athletes.”

No easy swim meets

The sport’s tremendous growth has been a boon in a competitive sense, ratcheting up the level of competition at all age groups as top swimmers from one team push those from others — whether NCAP, Rockville-Montgomery, Machine Aquatic or others.

Earlier this month, the region’s best age-group swimmers faced off with their counterparts from up and down the East Coast in the 10th annual Tom Dolan Invitational at the University of Maryland’s Eppley Center. Among them were Good Counsel’s Jack Conger, considered among the top recruits in the country, who’ll swim at Texas next season; Janet Hu, a junior who’s pegged as one of the top two or three recruits next season; Ledecky, the 2012 Olympic gold medalist in the 800 meters and the country’s top sophomore; and 12-year-phenom Cassidy Bayer, who has set age-group records in the butterfly.