Landscaping License Practice Test

If a 3/4-inch valve has a maximum flow of 10 gpm on a level area, what is the flow rate with a 25-foot elevation drop?

1. 5 gpm

2. 10 gpm

3. 15 gpm

4. 20 gpm

The correct answer is: 10 gpm

In this scenario, the maximum flow rate of 10 gallons per minute (gpm) for the 3/4-inch valve is specified under standard conditions on a level area. When considering the impact of an elevation drop, it's essential to understand how gravity affects fluid dynamics in a system. A 25-foot elevation drop introduces a gravitational potential energy that should theoretically increase the flow rate; however, the maximum flow rate of the valve is a critical factor that sets a ceiling on how much flow can occur through it. This maximum flow rate of 10 gpm is based on the sizing and design of the valve; it indicates that no matter the decrease in elevation, the flow cannot exceed this specified rate unless other factors like pipe sizing, friction loss, or additional pressure are taken into account. Since the question focuses on the flow rate with a 25-foot drop, but the maximum provided by the valve remains unchanged at 10 gpm, the correct response confirms that the flow rate will remain at the maximum value stated. Therefore, when asked for the flow rate with the elevation drop, the answer-upholding the maximum capability of the valve is clearly 10 gpm.