How Porta-Potties Work

By: Dave Roos

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!