Using the pumper rule of thumb, how many pumpers are typically needed for a system demand pressure of 450 psi?

Using the pumper rule of thumb, how many pumpers are typically needed for a system demand pressure of 450 psi?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (B)

The pumper rule of thumb estimates how many fire pumps are needed by assuming each pumper can contribute about 150 psi of discharge pressure. To meet a system demand pressure of 450 psi, you divide 450 by 150, which equals 3 pumpers. This quick estimate is commonly used in practice tests and initial sizing, though actual requirements can vary with friction losses, elevation, and pump performance curves.

The pumper rule of thumb estimates how many fire pumps are needed by assuming each pumper can contribute about 150 psi of discharge pressure. To meet a system demand pressure of 450 psi, you divide 450 by 150, which equals 3 pumpers. This quick estimate is commonly used in practice tests and initial sizing, though actual requirements can vary with friction losses, elevation, and pump performance curves.