What is the recommended minimum pressure of a fire hydrant?

• A. 10 psi
• B. 20 psi
• C. 30 psi
• D. 40 psi

Answer: (B)

The key idea is residual pressure during firefighting. When water is flowing from a hydrant, the pressure drops because of friction in the mains and hoses. You need enough pressure left to push water through the hose and nozzle so the stream remains effective. About 20 psi is the minimum residual pressure commonly recommended for firefighting operations, ensuring a usable stream even with some friction losses, elevation changes, and multiple hydrants in use. Pressures as low as 10 psi would weaken the stream too much, while 30 or 40 psi are higher-than-necessary minimums and depend on the system and fire demand.