Massachusetts Plumbers Journeyman Practice Exam

What is the minimum size required for the waste pipe connected to equipment in plumbing systems?

1. 1 inch

2. 1¼ inches

3. 1½ inches

4. 2 inches

The correct answer is: 1¼ inches

The minimum size required for the waste pipe connected to plumbing equipment is typically determined by the type of equipment and the volume of wastewater it handles. While various plumbing codes might specify different standards, the choice of 1¼ inches is commonly recognized as the minimum size for common plumbing applications, particularly for fixtures like sinks or lavatories. The selection of 1¼ inches provides sufficient capacity to avoid clogs and maintain proper drainage. Smaller pipes might not adequately support the flow from typical fixtures, as they could lead to blockages or reduced performance over time. This size balances the needs for adequate drainage while fitting standard equipment connections. In contrast, other sizes like 1 inch might be too small for most plumbing applications, and larger sizes such as 1½ inches or 2 inches may be used in different scenarios involving higher flow rates or more significant fixtures but are not the minimum requirement for standard waste connections. Thus, 1¼ inches is widely accepted for ensuring efficient waste removal in many plumbing systems while still being compatible with usual fixture settings.