Practice Question: Fire Hydrant Discharge to Atmosphere

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Solution

Step 1: Identify the known variables from the question
Outlet diameter \(D = 4 \text{ inches}\)
Pressure \(P = 50 \text{ psi}\)
Coefficient for a smooth and well-rounded outlet \(C_d = 0.90\)
 

Step 2: Plug the known values into the discharge formula
\[Q = 29.8 \times D^2 \times C_d \times \sqrt{P}\]
\[Q = 29.8 \times 4^2 \times 0.90 \times \sqrt{50}\]

Step 3: Perform the calculation
\[Q = 29.8 \times 16 \times 0.90 \times \sqrt{50}\]
\[Q = 29.8 \times 16 \times 0.90 \times 7.071\]
\[Q ≈ 3034.34 \ gpm\]

 

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