New York Low Pressure Boiler Certificate of Fitness (COF) Practice Test

What is the relationship in size between overflow pipes and supply pipes?

1. They must be the same size

2. Smaller, supply

3. Larger, supply

4. Depends on the system design

The correct answer is: Smaller, supply

Overflow pipes are designed to handle excess water that may result from overfilling or from thermal expansion within a boiler system. Since their primary function is to safely direct excess water away from the system, they do not need to accommodate the same flow rate as the supply pipes, which carry water into the system. Supply pipes are generally larger because they must facilitate the required flow of water to maintain the boiler's operation under normal circumstances, including during peak demand. The overflow pipe does not require that same capacity, hence it is appropriately sized to manage outflows, which are typically much less than the inflow through the supply pipes. In some systems, the overflow pipes may indeed be smaller than the supply lines, reflecting their different roles within the water management of the boiler system. Understanding this relationship helps ensure proper boiler operation and safety, where feeding the system adequately is critical, while managing excess is comparatively less demanding.