Which pipe configuration is commonly used for sewage in building plumbing?

The P trap is an essential component in building plumbing systems, specifically for sewage drainage. Its primary function is to prevent sewer gases from entering the living spaces of a building while allowing wastewater to flow through. The shape of the P trap, which resembles the letter "P", holds a small amount of water in its curve. This water acts as a barrier, sealing off the pipes and stopping unpleasant and potentially hazardous gases from escaping into the home or building.

In sewage systems, proper venting is also crucial, but the P trap specifically plays a vital role at every fixture's drainage point, such as sinks, toilets, and bathtubs. It ensures that wastewater is efficiently directed into the sewer system while simultaneously maintaining air quality within the building. Other options such as flat pipe, flexible pipe, and vented pipe systems may serve different purposes or applications within plumbing but do not fulfill the specific role of preventing sewer gas intrusion that is addressed by the P trap.