CSLB Class B General Contractor's License Practice Exam

What is the minimum size a water supply pipe to a building should be?

1. 1 inch

2. 3/4 inches

3. 5/8 inches

4. 1/2 inch

The correct answer is: 3/4 inches

The minimum size for a water supply pipe to a building is commonly established to ensure adequate water flow and pressure for various fixtures and appliances within the structure. A 3/4-inch pipe is typically selected because it provides a balance between sufficient water flow and the structural strength needed to handle the pressures in a residential or commercial building. This size allows for the efficient distribution of water, accommodating multiple fixtures without significant pressure loss or flow restriction. Having a pipe diameter of 3/4 inches helps to prevent issues such as low water pressure, particularly when multiple outlets are being used simultaneously. This size is also in line with many plumbing codes and regulations that dictate minimum requirements for water supply lines to ensure the safety and functionality of plumbing systems within buildings. Opting for larger sizes, such as a 1-inch pipe, may be unnecessary in most standard residential applications, while smaller sizes like 1/2 inch or 5/8 inches could lead to inadequate supply, especially in demand-heavy scenarios.