How Many Porta Potties Do You Actually Need?

Events: the published table

The portable sanitation industry publishes a two dimensional table, and it is a table rather than a formula for a good reason. Demand saturates. Doubling the length of an event does not double the units required, because the same guests cycle through. Unit count per guest also falls as crowds get larger.

These are the anchor numbers, for events without alcohol service:

The three adjustments

• Alcohol service. Add fifteen to thirty percent. An open bar sits at the top of that range, a beer-and-wine cash bar near the bottom.
• Accessibility. At least five percent of your total units accessible, minimum one. On twenty units that is one accessible unit. On forty it is two.
• Handwashing. One station per four toilets normally, one per two where food is being served. Every food vendor needs access to soap and running water.

Construction: one per ten, weekly

Jobsites use a completely different rule. The working standard is one unit per ten workers on a forty hour week, with service once a week. That ratio is what OSHA's construction sanitation standard, 1926.51, is generally satisfied by, and it is what every supplier will quote against.

Quote your peak crew, not your average. If you run twelve on framing weeks and thirty during a pour, order for thirty. Adding a unit mid-month costs a delivery fee. Running thirty people on two units costs you crew hours every day.

OSHA also requires potable water and washing facilities on construction sites, which is why a handwashing station or a combo unit belongs in the order rather than being treated as optional.

Peak load beats average load

The table gives you a number for the whole event. What actually creates a visible line is the surge.

Races are the extreme case: nearly the entire field needs a restroom in the same forty five minutes before the gun, and almost nobody does two hours later. That is why race planning runs one unit per fifty to seventy five participants, far denser than a general event of the same head count, and why the majority of the order goes at the start.

Festivals surge between sets and right after the headliner. Weddings surge at the transition from ceremony to reception and again after dinner. If your event has a hard schedule, look at where the crowd is all doing the same thing at the same time and size for that moment.

Placement changes effective capacity

Ten units in one row at the back of a field is not the same capacity as ten units in two clusters of five near where people already are. The second arrangement performs meaningfully better because walking distance is what determines whether someone joins the line or waits.

Cluster in groups of six to twelve near food, bars, stage exits and gates. Leave the service truck a route to each cluster that does not cross the crowd, which matters enormously on multi-day events.