A 2 ½ inch diameter pipe used as a combination waste and vent shall serve a maximum of how many fixture units?

• A. 4
• B. 5
• C. 6
• D. 7

Answer: (C)

In residential plumbing, a 2 ½ inch diameter pipe designated for use as a combination waste and vent can effectively handle a certain number of fixture units, which are a measure of the probable demand placed on the drainage system by various plumbing fixtures. The correct maximum number of fixture units for this size pipe is 6.

This number is determined based on standard plumbing codes, which outline the capacity of different pipe sizes regarding their ability to handle waste flow and venting requirements. A pipe's diameter significantly influences its capacity to convey both liquid and air, impacting the overall efficiency and performance of the drainage system.

Using a 2 ½ inch diameter pipe as a combination waste and vent maximizes the potential for adequate drainage while preventing issues such as siphoning or poor air circulation, which could lead to drainage system failures or unpleasant odors. Proper adherence to code specifications ensures that the plumbing system functions correctly and efficiently, contributing to the overall health and safety of the residential environment.