Which fixtures are required to have a trap in their drainage system?

In residential plumbing systems, all fixtures that discharge wastewater must have a trap in their drainage system. A trap serves crucial functions, primarily to prevent sewer gases from entering the living space by creating a water seal. This water barrier effectively blocks noxious fumes while allowing wastewater to flow through the drainage system.

Fixtures such as sinks, bathtubs, showers, and toilets are designed to produce wastewater, which requires an effective drain setup to ensure that the system functions properly and safely. Each of these fixtures generates waste that must be safely conveyed to the sewer or septic system, thus traps are necessary for all of them.

The other options suggest limited requirements for traps. Some imply traps are only needed for specific types of fixtures or none at all, which contradicts plumbing codes and best practices that mandate traps for all fixtures to ensure safety and proper operation of the plumbing system.