The total fall in a fixture drain due to pipe slope is limited to a maximum of __________.

• A. One pipe diameter
• B. Two pipe diameters
• C. Three pipe diameters
• D. Four pipe diameters

Answer: (A)

The total fall in a fixture drain due to pipe slope is limited to a maximum of one pipe diameter. This guideline is established to ensure that waste and drainage can flow effectively without creating excessive slope that can potentially lead to various installation or maintenance issues.

When the total fall is restricted to a single pipe diameter, it promotes adequate drainage by reducing the risk of material settling or blockage. A steeper slope can cause the liquid to move too quickly, leaving solids behind, which can result in clogs over time. Conversely, if the slope were too shallow, drainage may also be hindered. Therefore, limiting the fall to one pipe diameter strikes a balance that facilitates effective drainage while minimizing the risk of plumbing system failures.