What is the maximum allowable size of a single pressure tank in a standpipe/sprinkler system?

In a standpipe or sprinkler system, the maximum allowable size of a single pressure tank is governed by regulatory standards and design considerations. The acceptable limit is often determined by various codes, such as those proposed by the National Fire Protection Association (NFPA), which outlines safety and performance criteria for fire protection systems.

The choice of 9,000 gallons reflects the common regulatory frameworks that balance the need for sufficient water supply during a fire emergency while ensuring system reliability and manageability. This size ensures adequate pressure and capacity for effectively combating fires without placing undue strain on the infrastructure or posing excessive safety risks during operation.

The other sizes listed, while they may seem practical, exceed the typical limits set forth in standard practice and could lead to potential hazards in system design and operation. By keeping the maximum size at 9,000 gallons, it provides a safe and effective means of water supply under pressure for standpipe and sprinkler applications.