Under NFPA 20, where should a suction pressure regulating valve be installed?

Under NFPA 20, where should a suction pressure regulating valve be installed?

• A. Between back flow preventer and pump
• B. In the discharge line after the pump
• C. Inlet line before the back flow preventer
• D. Parallel branch with check valve

Answer: (A)

Suction side pressure control is about keeping the pump from cavitating by limiting how low the suction pressure can drop. The suction pressure regulating valve belongs on the suction line so it can regulate the pressure entering the pump. In NFPA 20 installations, install it in the suction line between the backflow preventer and the pump. This placement lets the valve sense and limit suction pressure while still preserving backflow protection. Putting it in the discharge line wouldn’t affect suction pressure; placing it in the inlet line before the backflow preventer could expose the valve to backflow conditions and lead to improper regulation; a parallel branch with a check valve would bypass the pump’s suction regulation entirely.

Suction side pressure control is about keeping the pump from cavitating by limiting how low the suction pressure can drop. The suction pressure regulating valve belongs on the suction line so it can regulate the pressure entering the pump. In NFPA 20 installations, install it in the suction line between the backflow preventer and the pump. This placement lets the valve sense and limit suction pressure while still preserving backflow protection. Putting it in the discharge line wouldn’t affect suction pressure; placing it in the inlet line before the backflow preventer could expose the valve to backflow conditions and lead to improper regulation; a parallel branch with a check valve would bypass the pump’s suction regulation entirely.