NFPA 13D fire sprinkler systems on well water
Well systems incorporating fire sprinklers at the start of the building process are set up to effectively address this fire protection application. The following will explain how NFPA 13D systems are integrated into well systems.
Water sits in three areas in a well-fed system: in the well above the pump, refilling into the well as it is used, and in the holding tank in the home. NFPA 13D states that the refill rate can be counted on to help supply part of the demand, and therefore, the duration demand of 7 or 10 minutes can be met by the sum of these three sources. The refill rate can be determined by the person that drills the well.
Wells are set up at the inception of the home building process and a larger well pump is usually installed along with larger expansion tanks. Homes on well water most likely will need a pump to serve the domestic water supply. The cost associated with providing additional pressure to run the fire sprinkler system may simply be the difference between the regular pump the homeowner must install to obtain the necessary pressure for domestic use, and a higher flow pump, or a booster pump and tank.
Residential pump and tank manufacturers tell us that the expansion tanks are sized to pick up the difference between the well capacity and demand so they are not necessarily as large as some would believe. To meet the requirements of NFPA 13D, many installations have been done using this method, effectively and cost competitively.
According to NFPA 13D, where a pressure tank is used for the water supply those who meet the requirement of ASME Boiler and Pressure Vessel Code are acceptable, provided the authority having jurisdiction considers the air or nitrogen supply reliable.
Stand alone tank systems are similar to the pressurized tank systems in that they can be set up to provide for the difference in supply as opposed to total demand. According to manufacturers, generally for little extra cost, total demand can be covered. They say that stagnation is easily addressed during testing, and that no problems have been identified. They advise that a separate pump is required but is also for relatively low cost and highly competitive. It has the benefit of not being used for anything but the fire demand, so the system is never compromised.
Stand-by power is not required by code, but many manufacturers build their systems with battery back-up as a standard feature. They posit that frequent maintenance is not required on these systems. It consists of periodic checks that are neither difficult nor time consuming.
According to General Air Products, one of the manufacturers consulted in order to address this technical issue, they “sell systems every day to meet the varying demands of the marketplace. Every situation is not the same but we have yet to find a scenario which cannot be addressed technically or cost effectively.”