Plumbing Fixture Unit Standards

Plumbing fixtures on a white background.

Each plumbing fixture in your home must meet a water unit standard. These were established to ensure safety and consistently measurable water volume flow, and to minimize contamination of drinkable water by water already used for other purposes. Learn more about plumbing fixture unit standards below.

Plumbing Fixtures

Plumbing fixtures include toilets, bidets, urinals, sinks, showers, bathtubs, lawn sprinklers, and laundry tubs attached to clothes washers. In order to determine the billing for water use for each household, the number of each of these fixtures in a household must be counted, and the allowable water discharge or flow of each tabulated on a Water Usage form.

Plumbing Fixture Unit Standards

A toilet surrounded by tools.

The unit standards for each plumbing fixture set the maximum amount of water that each can use and the maximum water flow rate as applicable. In many municipalities the following standards have been set for particular fixtures:

  • Water discharge from toilets cannot exceed 3.5 gallons for each flush.
  • Water discharge from urinals cannot exceed 1.5 gallons with each flush.
  • Water rate for showers must be below 3.5 gallons per minute under pressure.
  • No plumbing fixture is permitted that has a continuous flow rate/ one that cannot be shut off.

In municipalities with seasonal water scarcity problems, these standards may be reduced during those times of year.