How many traps are required if storm piping runs separately from sanitary piping?

In plumbing design, a trap is typically used to prevent sewer gases from entering a building while also allowing wastewater to flow through. When storm piping and sanitary piping run separately, it is crucial to understand the function of each system.

In scenarios where storm drainage systems are distinct from sanitary drainage systems, the traps are identified based on the function of the drainage system involved. Sanitary traps (such as those in sink drains, toilets, etc.) are critical for the sanitary piping, particularly to manage waste flow and odor. Conversely, stormwater systems are generally designed to handle rainfall and surface water without the necessity for traps, as they do not typically carry waste that requires the same protection against sewer gas escape.

Therefore, if storm piping runs separately from sanitary piping within a plumbing system, only one trap is necessary for the sanitary system to prevent sewer gases from entering living spaces. Stormwater does not necessitate a trap, hence it is only the sanitary drainage that is required to have one trap in this scenario. This understanding aligns with the plumbing codes and practices regarding waste and venting systems, showcasing the importance of efficient separation and function in plumbing design.