How Porta Potties Work: The Simple System Behind the Plastic Booth

A different kind of toilet

Conventional toilets use water, pressure and gravity to move waste through a trap and into plumbing. Portable toilets have no plumbing, and their waste collects in a tank beneath the seat.

The standard plastic unit is made from large, rigid panels designed to be weather- and insect-proof, easy to clean and lightweight to move. George Hardig filed a patent for porta potties in the late 1960s, and later co-founded PolyJohn Enterprises.

Inside the holding tank

In a typical unit, waste drops into a tank that averages 25 to 30 gallons. The tank contains about five to 10 gallons of water, along with a dark-blue chemical mixture.

The chemicals help control odors, begin breaking down waste and toilet paper, and conceal the tank’s contents. Walt Terry, director of operations for Metro Services, says the mixture can turn green when it is no longer working.

A vent pipe near the back of the roof draws gases from the tank and releases them into the air. Some models also have urinals that direct urine into the holding tank.

How units are serviced

When a unit needs servicing, trained rental-company employees arrive with a vacuum truck. They use a hose to remove liquids and solids from the holding tank and transfer them into the truck for disposal.

Many vacuum trucks also carry clean water in a separate compartment, which staff use to wash out the porta potty. The account ends before explaining what happens after that cleaning step.