A “halftime flush” (or “Super Bowl halftime flush”) is when the television viewers of a widely watched sporting event (such as the football’s Super Bowl or soccer’s World Cup) all go to the bathroom at the same time during halftime. This puts pressure on a city’s water mains.
 
The term “Super Bowl flush” was used in 1984, when Super Bowl halftime flushing was blamed for a water main break in Salt Lake City, Utah. It’s still unclear if the Super Bowl was the cause. “Super Bowl Halftime Flush” was cited in print in 1999 and “halftime flush” in 2006. “Halftime flush” was discussed in 2014 regarding soccer’s internationally popular World Cup matches.
 
 
Google News Archive
24 January 1984, The Times-News (Hendersonville, NC), pg. 13, col. 1:
Super Bowl flush
SALT LAKE CITY—The rush to bathrooms during halftime of Super Bowl XVIII has been blamed by a water department supervisor for the rupture of a 16-inch water main.
(...)
The cause of the break may never be determined officially, but Stevens said as far as he’s concerned, it was due to too many fans flushing their toilets at the same time.
   
Google News Archive
22 January 1990, Spokane (WA) Chronicle, “Super Bowl excites advertisers” by Skip Wollenberg (AP), pg. A9, col. 5:
Sterling Drug Co.  ran a promotion in nine cities this fall that it called the “Phillips’ Milk of Magnesia Super Bowl Flush.” Radio announcers asked listeners to name the activity most frequently performed during the Super Bowl. Those who called in to say “toilet flushing” were entered in a sweepstakes with nine winners getting trips to the Super Bowl.
     
Google Groups: alt.impeach.clinton
Would you resign if you were him?
Thomas Pain
1/13/99
I’m real frustrated by this guy clinton and the apparent support represented by the Polls.  I’ve come up with a way to conduct a poll that can’t be spun by the libs/media and I’d like your opinion, or a better suggestion if you have one to show how little support clinton actually has.
 
I’m suggesting that on the night of his “State of the Union” speech we all do a “Super Bowl Halftime Flush” on him commencing the moment he begins to speak. When he starts we should all flush our toilets & turn on all our faucets for a couple of minutes to signal our disdain for him.  The resulting water pressure drop would send a strong signal to the Senate that we want him “flushed” out of office.
 
28 January 2001, Rockford (IL) Register Star, “Tackle some trivia before the big game” (Gannett News Service), pg. 3C, col. 2:
Myth 1: With so many viewers running to the bathroom during halftime, a phenomenon known as the “Super Bowl Flush” threatens to wreak havoc with municipal sewer systems.
 
In truth, the only record of a major water main break during a Super Bowl halftime was in 1984 in Salt Lake City, when a 16-inch pipe burst. LeRoy Hooten Jr., the city’s director of public utilities, explains how the legend started: “I was in my car and had the work radio on, and as I recall, the standby foreman jokingly said (the break) was caused by the Super Bowl Flush. At the time, I didn’t think it was related. it was just something to chuckle over. But it got picked up and never did get disputed.”
   
4 February 2006, Salina (KS) Journal, pg. C6, col. 1:
Super Bowl myths don’t really hold up
Most city sewer systems able to handle halftime flush
By MIKE LEWIS
Seattle Post-Intelligencer
   
Twitter
James Williams
‏@pasadenalive
The Legend of the Halftime Flush Is Silenced by Waterfree “Urinal of Champions” (Marketwire) http://bit.ly/7ufHdR
11:35 AM - 28 Dec 2009
 
Twitter
Scott Huler
‏@huler
The great Super Bowl flush is a myth, but the East Enders kettle surge? True: http://bbc.in/8XJepN. it’s all about #infrastructure #scio11
12:12 PM - 20 Aug 2010
 
L.A. Weekly (Los Angeles, CA)
L.A. Water Use Jumped Due to World Cup “Halftime Flush”
By Gene Maddaus Fri, Jun 27, 2014 at 7:01 AM
In perhaps a sign of the growing popularity of soccer in the United States, the L.A. Department of Water and Power recorded a modest spike in water usage at halftime of Thursday’s World Cup game between the U.S. and Germany.
 
Water usage then dropped sharply during the second half. It spiked again when Angelenos went to the bathroom en masse at the conclusion of Germany’s 1-0 win. The chart above is from readings taken at the DWP’s Franklin Canyon Reservoir.
 
The “Super Bowl Flush” is well documented, so this is not exactly a surprise. And the peaks at the right of the chart are dwarfed by the peaks at 6 a.m. and 7 a.m. - which apparently are the two most popular wake-up times in L.A.