What diameter and length of a dirt pocket is required when a drop line is 3-inch diameter?

The correct answer indicates that a dirt pocket for a 3-inch diameter drop line should have a diameter of 2 inches and a length of 3 inches.

In the context of piping and system design, dirt pockets are often incorporated into systems to collect sediments or debris from the fluid transported through the pipes. The size of the dirt pocket is dependent on the diameter of the pipe it serves. A dirt pocket should be somewhat smaller in diameter than the pipe to ensure that it effectively funnels sediment towards the lower point of the pocket without creating excessive obstruction or flow resistance.

In this case, a 2-inch diameter dirt pocket is proportional to the 3-inch drop line, allowing it to capture debris while also maintaining flow characteristics of the system. The length of 3 inches is appropriate to provide enough space for debris accumulation without significantly affecting the overall flow dynamics in the system.

Setting the diameter too close to the drop line's diameter could result in ineffective sediment collection and potential blockages, while a significant deviation below the required size could lead to insufficient volume for sediment accumulation. Thus, a balance must be struck, which is exactly what is achieved with a 2-inch diameter and 3-inch length dirt pocket.