How Porta-Potties Work

By: Dave Roos
Two men dash across the tops of porta-potties in the infield at the Kentucky Derby at Churchill Downs, 2008. The porta-potty race is an unofficial Kentucky Derby tradition.
Jason Sankovitch/Lexington Herald-Leader/MCT via Getty Images

At the weeklong Taste of Chicago festival held every July, more than a million people swarm Chicago's lakeside Grant Park to consume large quantities of digestibly combustible food like slow-roasted Cuban pork tamales, bacon on a stick, Italian sausage sandwiches, sautéed goat with plantains and braised oxtail poutine.

If you're curious, there are only a handful of bathrooms in Grant Park in the vicinity of the festival [source: Chicago Park District]. Time to call in the poop pros.


In 2014, the veterans at Service Sanitation Inc. won the contract to provide porta-potties — "portable sanitation equipment" in industry lingo — for the Taste of Chicago. After consulting with event organizers, the crew trucked in 380 regular porta-potties, 28 wheelchair accessible units, and 80 hand-washing stations with soap and fresh running water [source: Dageforde].

Every night from 9 p.m. to 3 a.m., Service Sanitation arrived with tanker trucks and vacuum pumps to suck up the day's waste and refuel the porta-potties with fresh toilet paper and pungent blue chemicals [source: Dageforde]. By morning, the units were primed and ready for another big day of eating and evacuating!

Portable bathrooms go by many names: porta-potty, porta-john, jiffy-john, porta-loo (UK) and toi-toi (Malaysia). And portable sanitation companies certainly have a way with puns; "No one takes care of business like Mr. John!" or the classic, "We're No.1 in the No. 2 business!"

While you're most likely to find portable bathrooms at large outdoor events like food festivals, county fairs and rock concerts, they're also required by law at most construction sites and a matter of urgent necessity just about anywhere there isn't a dedicated restroom: parks, hiking trails, roadside food stands and ball fields.

Porta-potties aren't pretty, but they are simple, well-built structures that fulfill a critical societal function. And as repulsive as it seems to fill a stationary tank with human waste and suck it up with a vacuum once a week, portable toilets save a lot of water — an estimated 45 billion gallons (170 billion liters) a year [source: PSAI] — and beat the heck out of squatting in a field.

Evolution of Portable Toilets

Modern portable bathrooms have come a long way since the Strongbox.
Benjamin Rondel/Getty Images

Porta-potties are different than outhouses. Outhouses and other types of "outdoor plumbing" have been around for centuries and amount to a semi-permanent structure placed over a deep earthen pit. Portable toilets, on the other hand, are self-contained units where human waste is stored temporarily in a holding tank and removed by some very dedicated people.

Like many other technological and engineering innovations of the 20th century, the portable toilet was born during World World II. The 1940s war effort required sturdy and sanitary temporary toilets that could be erected while constructing military bases or moving personnel into areas lacking infrastructure [source: PSAI].


Early generations of porta-potties were big, heavy structures made out of wood or metal, and were a challenge to transport from site to site. The rise of plastics and other strong, lightweight polymers revolutionized the industry. Porta-potty pioneer Harvey Heather is credited with designing the first one-piece fiberglass unit, called the Strongbox, in the late 1970s [source: Kneiszel].

The fiberglass Strongbox was just as sturdy as wood or metal, but much easier to clean and lighter to transport. But the one-piece molded design also had its drawbacks. The thick, dark material didn't let in any natural light, and the units weren't designed to be stackable on flatbed trucks, which increased the cost of transport from factory to customer [source: Kneiszel].

Modern portable bathrooms have come a long way since the Strongbox. Today's standard porta-potty has a white translucent roof to let in natural light, a non-slip floor to prevent accidents, and a ventilation system designed to route nasty odors up and out of the holding tank. Basic models even have a separate urinal and an antibacterial gel dispenser for improved sanitation.

Some construction sites require specialty potties. What if you're working 40 stories up on a high-rise and nature calls? A unit called a "roll-around toilet" is a miniature porta-potty on wheels that can easily fit into a construction elevator or be hoisted by a crane.

There are also luxury and executive models for upscale outdoor events. Often called restroom "trailers," these larger units feature flushable porcelain toilets, partitioned stalls, sinks with running water and amenities like mirrors and hand towels.

Next we'll answer the million-dollar question: 'What's inside the tank?

What's Inside the Tank?

First rule of using a porta-potty — never look inside the tank. There aren't' enough chemicals in the world to cover up the unmistakable sight and smell of a pile of human waste. But that's exactly what the blue liquid inside every porta-potty is trying to do.

There are three main ingredients in the traditional chemical cocktail poured into the holding tank of a porta-potty:


  • Blue dye to hide the appearance of the waste
  • Fragrance to mask the odor
  • Biocides to kill bacteria and microbes

For decades, the industry standard for killing bacteria in porta-potties was formaldehyde, the same potent chemical used to preserve tissue samples and embalm corpses. But an increasing number of states have outlawed formaldehyde in portable toilets, because wastewater treatment plants aren't equipped to properly dispose of the chemical, a known carcinogen [source: CEPA].

The phasing out of formaldehyde has led to the development of "greener" solutions for porta-potty chemicals. Instead of killing off all microbial life in the tank, the green approach is to introduce beneficial enzymes and microbes that feed on odor-causing bacteria. Some biological additives even speed up the decomposition of organic matter, including toilet paper, which means that tanks don't need to be emptied as often.

Weather can mess with porta-potty tanks. When it's hot outside, it's even hotter inside the bowels (literally) of the potty. And when temperatures soar, bacteria go into overdrive, meaning things get very stinky very fast. To combat this, porta-potty operators bump up the ratio of chemicals to water in the summer, and also when a unit is expected to receive heavy use, like at a festival.

Frozen turds are equally bad. How do you clean out a unit when the tank is a putrid block of ice? In the depths of winter, porta-potty operators add a salty brine to lower the freezing point of the tank. A nifty trick for keeping the brine ratio correct is to add a cake of rock salt to the urinal. As patrons use the urinal, the cake slowly releases more salt into the tank [source: PRO]. Brilliant!

Servicing Porta-Potties

Glastonbury Festivalgoers wait for the portable toilets to be cleaned in Somerset, England.
Martin Godwin/Getty Images

Cleaning out a porta-potty has to be one of the world's worst jobs, right behind ... wait ... nope, that's actually the worst one. On a typical day, a portable sanitation worker will service 40 to 50 different units [source: Cutter]. "Servicing" is a euphemism for sticking the business end of a vacuum pipe down into the unholiest of unholies and sucking up the contents.

The porta-potty vacuum is attached to a tanker truck equipped with a large waste storage unit and a smaller freshwater tank. Once the contents of the potty are removed, the sanitation worker fills the tank with a few buckets of freshwater and then adds the required squirts of blue goo or a pre-measured packet of dry solution.


Sadly, cleaning out the holding tank is often the least disgusting part of a porta-potty worker's job. People, you see, are filthy animals. They will deposit waste where no waste should ever be deposited: next to the seat, on the seat, in the urinal, on the floor, on the walls and on the ceiling (don't ask).

People will also drop all sorts of non-crap "crap" into the tank, where it's destined to clog the vacuum. One anonymous porta-potty worker wrote about finding cell phones, glasses, lots of drug paraphernalia, the occasional lethal weapon and the sadly less occasional wallet full of cash or expensive piece of jewelry floating in the blue poop swamp.

The prize for absolute worst-case scenario goes to the tipped over porta-potty. Storms, errant vehicles and hilarious pranksters will sometimes knock over a portable toilet, but the real nightmare is when it tips over on its door. In that situation, the worker has to lift up the unit as a tidal wave of waste pours out, coating every internal surface. The worker will actually have to step inside the poop-marinated box to clean some hard-to-reach areas [source: Cutter]. Oh boy.

Porta-potty vacuum tankers deliver their horrible contents to municipal wastewater treatment plants, where it is added to the rest of the sewage sludge. Each porta-potty unit is serviced on a weekly basis, or more often in high-use areas. So next time you see one of these trucks on the road, give the driver an appreciative wave. He deserves it!

Lots More Information

Author's Note: How Porta-Potties Work

You get to spend a lot of quality time in portable bathrooms when you start potty-training your children. Kids have an uncanny ability to wait until you are the furthest distance from a clean, comfortable bathroom before alerting you that they have to "make poopy." During the past 10 years of potty training three kids, I guarantee that I've visited every porta-potty in my tri-county area. In most cases, they have been perfectly clean, or at least as clean as such a structure can reasonably get. But you never get over the smell. And as thankful as I am for the complimentary hand sanitizer dispenser found in most porta-potties, there are some experiences — like when your toddler tells you a little too late, for example — that no amount of hand sanitizer can wash away.

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More Great Links

  • California Environmental Protection Agency. "Formaldehyde" (July 26, 2015)
  • Chicago Park District. "Grant Park" (July 26, 2015)
  • Cutter, Chip. "Port-a-potty cleaning not such a foul job after all." Indianapolis Business Journal. July 14, 2008 (July 26, 2015)
  • Dageforde, Betty. "Service Sanitation Provides Restrooms for Taste of Chicago's Feeding Frenzy." Portable Restroom Operator. June 2015 (July 26, 2015)
  • Kneiszel, Jim. "He Called it the Strongbox." Portable Restroom Operator. March 2010 (July 26, 2015)
  • Mannen, Amand; and Anonymous. "We Find Corpses: 5 Weird Truths of Cleaning Porta Johns." Cracked. June 24, 2015 (July 26, 2015)
  • Portable Restroom Operator. "Avoid Ice Cube Holding Tanks." Feb. 2009 (July 26, 2015)
  • Portable Sanitation Association International. "PSAI Global Sanitation Education Initiative" (July 26, 2015)
  • Portable Sanitation Association International. "PSAI's 40-year history is rich with innovation and tradition" (July 26, 2015)
  • United Site Services. "Bronze Heavy-Duty Restroom Trailers" (July 26, 2015)
  • United Site Services. "Bronze Heavy-Duty Restroom Trailers" (July 26, 2015) United Site Services. "Roll-Around Toilet" (July 26, 2015)