Which minimum pipe size is used for residential area distribution?

• A. Six
• B. Four
• C. Eight
• D. Ten

Answer: (A)

The main idea is that the distribution piping in a residential area must be large enough to carry the expected fire-flow without dropping pressure too much. Six inches is used as the minimum because it provides enough capacity to serve typical residential hydrant demands while keeping friction losses manageable. A four-inch main would quickly lose pressure under fire-flow conditions, making hydrants difficult to use effectively. Larger sizes like eight or ten inches aren’t usually necessary for standard residential distribution and would add unnecessary cost without a corresponding benefit in typical layouts.