Firefighter Practice Exam

What is the friction loss in psi for 150 feet of 1 ½ inch hose if the loss for 100 feet is 25 psi?

1. 16.67 psi

2. 37.5 psi

3. 47.3 psi

4. 52 psi

The correct answer is: 37.5 psi

To determine the friction loss for 150 feet of 1 ½ inch hose, one must first understand the relationship between hose length and friction loss. Friction loss is commonly calculated using a formula that indicates that loss occurs over a set distance of hose. In this case, we know that for 100 feet of hose, the friction loss is 25 psi. Since the loss is proportional to the length of the hose, it can be calculated by first finding the loss per foot. Dividing the total loss for 100 feet (25 psi) by 100 gives a friction loss of 0.25 psi per foot. Next, to find the loss for 150 feet, you multiply the loss per foot (0.25 psi) by the total length in feet (150): 0.25 psi/foot × 150 feet = 37.5 psi. This indicates that the friction loss for 150 feet of 1 ½ inch hose is indeed 37.5 psi. This value is consistent with standard practices in firefighting where longer lengths of hose lead to increased friction loss, necessitating calculations to determine the pressure needed at the source to maintain adequate flow at the discharge end.