What is a common requirement for plumbing drains according to the code?

A common requirement for plumbing drains according to the code is that they must be vented. Venting is essential as it allows air to enter the drainage system, which helps to maintain neutral air pressure in the pipes. This process prevents the formation of vacuum conditions that could impede the flow of wastewater, potentially causing blockages or siphoning of water from traps. Proper venting is crucial for the overall function and safety of the plumbing system, as it also helps to prevent sewer gases from entering living spaces.

In contrast, while specific installation angles may be recommended for certain applications to ensure effective drainage, a uniform requirement for a 45-degree angle is not standard. Additionally, drains are typically designed to accommodate connections from multiple fixtures; thus, the restriction to connect only one fixture is not a standard code requirement. Lastly, although PVC is a common material used for drains, the code does not mandate that drains be made of PVC exclusively, as there are various approved materials available for different plumbing applications.