A. Distribution pipes used in trenches or beds for gravity distribution must be at least 4 inches in diameter, and must be constructed of sound and durable material not subject to corrosion or decay or to loss of strength under continuously wet conditions; and

B. Distribution pipes used for gravity distribution must have 1 or more rows of holes of no less than 1/2-inch in diameter, spaced no more than 40 inches apart. Holes must be spaced to prevent failure due to loads.