Water Supply Capacity, Pressurization, and Reliability

Fundamental to the use of fixed water-spray systems and other water-based extinguishing systems is a water supply that is adequate in terms of capacity, pressurization, and reliability. The capacity available may come from bodies of water, domestic supplies, and/or tank storage. A system s adequacy must be judged on the basis of its projected maximum flows, the duration of its flows, and the volumes necessary to meet industrial needs. The latter is relevant in cases where there is no dedicated supply. 

Water pressure is a key consideration in terms of the adequacy of application and system operation and maintenance. While some domestic supplies have high pressure systems, most are in need of pressurization, as is water from bodies of water and tanks. Fire pumps are routinely used, most often in multiple installations with different means of power drive (e.g., electric, diesel, or steam). When fire pumps operate at high pressures, there is the potential for leaks and line fracture. Periodic maintenance, including hydrostatic testing, will help minimize the potential for such failures. 

Most large and complex facilities have multiple sources of water, often from different supplies. Multiple pumps with different power sources are typically installed in parallel to ensure reliable operation in case of a pressure drop. Other reliability considerations include the variability in natural water supplies during different times of the year, for example, fall drought conditions, ice formations, and also the condition of water intakes, for example, trash buildup. 

Hydraulic calculations of water supply systems are critical to confirming their adequacy. Often such calculations are not current and, hence, flows and pressures are not readily available to be used as part of evaluations of system performance in cases where different events necessitate their use. 

Overall system maintenance is key to ensuring adequate and reliable water flows. Constant water levels, open and operable control valves, and fire pumps that are maintained and tested periodically, are some of the requirements that must be addressed as part of a long-term program. 

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