The Super Flush: A myth that won’t go down the drain

Brightwater Treatment Plant’s Main Control is set up with many screens to monitor aspects of our system in real-time.

Every year, as millions gather for the Super Bowl, an old urban legend resurfaces. It might be the first time you’ve heard it, but in our line of work, it’s a tired tale. Legend has it that when Super Bowl halftime comes around, everyone will use the restroom at the same time, sending down a “super flush” that wastewater treatment plants just can’t handle.  

It’s wild to think of everyone flushing at once, sending a huge rush of water through the pipes. But the truth is, the system is built for much bigger challenges.

Big pipes for big flows, this historic photo is from the construction of West Point Treatment Plant in 1966.

Our system can handle the blitz  

King County’s wastewater system was built to handle some serious flow. Our pipes and treatment plants don’t just manage the daily ebb and flow of showers, dishwashing, and regular bathroom visits. They are designed with extra capacity for major surges, like heavy rainstorms. Check out more about our combined wastewater-stormwater sewer system here. 

We know our system can handle it because we check and measure the flow all the time. We have a dedicated team of flow monitoring specialists who track the movement of wastewater through the system around the clock. Their job is to make sure everything is running smoothly and to catch potential issues before they become problems.

On a good day, we stay topside, but occasionally, the job calls for some thorough investigation.

Our specialists track wastewater movement in our pipes and around treatment plants using a number of high-tech tools, some of which include:  

• Ultrasonic sensors – Measure water depth without contact.  
• In-pipe submerged velocity sensors – Track water speed inside pipes.  
• Radar-based sensors – Combine radar and ultrasonic technology for precise water depth and speed monitoring.  
• Bubbler systems – Measure water levels in combination with engineered structures like weirs and flumes.  
• Magnetic (Mag) meters – Measure flow in closed (or pressurized) pipes.  
• Data loggers – Collect and store flow data. 
• Remote monitoring systems – Provide real-time data to detect issues early 

Admittedly, these are a bit heady and maybe a topic for another story! Using this technology helps us plan for system upgrades, prevent backups, and make sure we can handle everything from daily usage to major storms.  

What the data tells us  

West Point Treatment Plant, which handles all of Seattle’s wastewater, typically processes 133 million gallons of wastewater per day in February. But it can handle an instantaneous maximum of more than three times as much at 440 million gallons per day. Across King County’s three major treatment plants, the system can handle up to 865 million gallons per day. That’s close to 10,012 gallons per second!  

You can see that when the weather is dry, we typically see flows ramp up as people start their day and remain steady throughout the day before dropping at night. Toward the end of this chart, flows start to increase as we treat the recent rain and snow. Final effluent refers to the treated water that is discharged from our plant.

So, is a Super Bowl halftime bathroom break even noticeable?  

“If we dig into our flow monitoring data, we probably could detect a slight uptick, but it isn’t anywhere near volumes that could overwhelm our system — not even close,” says Mckenzie Mell, a flow monitoring lead for King County’s Wastewater Treatment Division. “If we can handle a week of relentless Seattle rain, a few extra flushes are no big deal.”

Yeah, that’s a big pile of “flushable” wipes and rags we fished from one of our pumps. When we say they don’t break down, it means they really don’t break down!

Don’t fumble your flush 

The real problem for wastewater systems is not a halftime flush. It is what people put down the drain.  

“One of the biggest issues are wipes that claim to be flushable,” Mell says.  

Unlike toilet paper, these disposable wipes do not break apart in water (despite saying they are flushable on the packaging). They get caught in pipes, jam pumps, and create massive blockages that cost time and money to remove.  

“And wipes are not the only issue. Tampons, paper towels, cotton swabs, and anything that is not toilet paper, pee, or poop should go in the trash. Even if a product says it is safe to flush, it can still cause problems in the wastewater system.”  

So, a halftime flush won’t break the system, but bad flushing habits might. The real way to help keep wastewater flowing smoothly is to be smart about what goes down the drain.