What factor is most important when selecting pipe size for a plumbing system?

When selecting pipe size for a plumbing system, water supply pressure is the most important factor because it directly influences the flow rate of water through the pipes. Adequate water supply pressure is crucial to ensure that fixtures receive enough water flow for optimal performance. If the pipe diameter is too small, it can restrict the flow, leading to inadequate pressure at the fixtures and poor performance during use. Conversely, a larger diameter pipe can accommodate higher flow rates, but if the water pressure is low, it may not make a significant difference in performance.

While other factors such as distance to the fixture, type of material, and temperature of the water also play a role in the overall plumbing system design, they do not have as direct an impact on the flow rate as water supply pressure. For example, although distance can affect the amount of pressure loss due to friction in the pipe, ensuring that the initial pressure is sufficient is a primary consideration. The material of the pipe may determine longevity and resistance to corrosion, but it does not dictate the necessary size for maintaining proper flow under pressure. Similarly, temperature might affect the type of pipe material selected, but it is not a determining factor when it comes to initial pipe sizing related to flow. Thus, prioritizing water supply pressure