Georgia Septic Installer Practice Test

For a fluid velocity of 30 gallons per minute, what is the minimum size pipe required?

1. 1 1/2 inch

2. 2 inch

3. 2 1/2 inch

4. 3 inch

The correct answer is: 2 1/2 inch

To determine the minimum size pipe required for a fluid velocity of 30 gallons per minute (GPM), it is essential to reference hydraulic principles and the corresponding pipe sizing charts. For gravity-fed systems, the selection of the pipe size is influenced by the desired flow rate and the fluid velocity. A standard guideline for fluids is that the velocity in the pipe should not exceed certain thresholds, commonly around 2 to 10 feet per second (fps), depending on the type of fluid and its application. In domestic septic systems, maintaining proper fluid velocity helps prevent issues like solids settling and clogs. Given the flow rate of 30 GPM, calculating the necessary pipe size involves converting gallons per minute to cubic feet per second for more precise analysis, as this helps in checking various charts that correlate flow rates with pipe diameters. For instance, 30 GPM translates roughly to 0.067 cubic feet per second. Using pipe diameter tables that consider standard flow rates, a diameter of 2½ inches effectively accommodates the desired velocity while maintaining efficient fluid movement without excessive pressure loss due to friction. This is particularly crucial in a septic system, where consistent and unobstructed flow is essential for proper functioning. A pipe of this size would allow the liquid