It is standard practice not to reduce incoming supply pressure below how many psi?

• A. 15
• B. 25
• C. 30
• D. 20

Answer: (D)

Maintaining a minimum intake pressure is essential to keep the pump from losing prime and to prevent cavitation on the suction side. Keeping incoming supply pressure at or above twenty pounds per square inch gives the pump enough net suction head to overcome friction losses and avoid drawing air through leaks or fittings. If the intake falls below twenty psi, prime can be lost and flow can drop due to cavitation, compromising the fire stream. Therefore, the standard practice is not to reduce incoming supply pressure below twenty psi; higher pressures are fine, but twenty psi is the critical minimum.