TANDEM PUMPING
When operating hoselines from standpipe systems having either plain hose valves, overriding-type pressure-restricting valves, or removable pressure-restricting devices, it usually is an easy matter for a single pumper to supply the volumes and pressures needed by suppression crews operating on the upper floors; these control devices are installed on standpipe systems having a maximum operating pressure of 175 psi.
High-pressure standpipe systems that have riser pressures of up to 600 psi must have pressure-regulating valves (PRVs) installed to safely reduce high-riser pressures to around 100 psi at the hose outlet. It is important that the fire department inspect each standpipe system installed in its jurisdiction and make note of the pressure at which each operates. In the event of building fire pump failure, the department must supplement the system through the standpipe Siamese. Unless die designed operating pressure for the building’s system is maintained, the PRVs will not function properly and will not supply the necessary water.
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