Which units are used to describe flow and pressure in sprinkler design?

• A. Gallons per minute and pounds per square inch
• B. Liters per minute and kilopascals
• C. Cubic meters per hour and bars
• D. Gallons per day and pounds per square inch

Answer: (A)

The key idea is that sprinkler design specifies how fast water can flow and the pressure available to push it through the system. Flow is a rate of water volume per time, and the common unit for this in sprinkler design in the U.S. is gallons per minute. Pressure is the force per area, and pounds per square inch is the standard unit used to express that pressure in typical design work and NFPA calculations.

This pairing—gallons per minute for flow and pounds per square inch for pressure—fits the conventional practice, making it easy to read pump curves, calculate friction loss, and size components consistently. While metric units exist (liters per minute, kilopascals or bars), they are not the standard in many sprinkler design contexts in the U.S. The other options mix metric units or use a non-rate like gallons per day, which doesn’t describe flow properly.