What is the realistic minimum usable residual pressure from a water distribution system for firefighting operations?

The realistic minimum usable residual pressure from a water distribution system for firefighting operations is 20 PSI. This pressure level is considered critical because it represents the lowest pressure at which adequate water flow can be maintained to effectively combat a fire.

At 20 PSI, firefighters can ensure they have sufficient water supply to operate handlines and other firefighting equipment, such as nozzles, which typically require a minimum pressure to optimize their performance and allow for effective stream reach and pattern. It also ensures that the water supply can support any additional friction loss incurred through hoses and fittings during firefighting operations.

Lower pressures, such as 10 or 15 PSI, may not provide enough force to push water effectively through hoses or maintain an adequate flow rate to extinguish a fire, leading to compromised firefighting efforts.