What is the required slope for distribution pipes per 100 feet?

• A. 0 to 1 inch
• B. 1 to 2 inches
• C. 2 to 4 inches
• D. 4 to 6 inches

Answer: (C)

In irrigation distribution design, you want enough slope to overcome friction along the line and keep water moving at a steady, self-cleaning velocity so sediments don’t settle and block outlets. The recommended slope for distribution pipes is two to four inches of drop per 100 feet. This range balances keeping the flow moving with reasonable pressure loss, ensuring all zones receive water fairly.

If the slope is too shallow (0 to 1 inch per 100 feet), flow slows and sediments can settle, leading to clogs and uneven distribution. If the slope is too steep (4 to 6 inches per 100 feet), the flow velocity increases significantly, raising energy costs and potentially causing excessive pressure variations at distant outlets.