Reservoir Size for Sprinkler System
Reservoir Size for Sprinkler System
(OP)
I have large building with a number of sprinkler headers located at various locations. The building fire protection system is to be supplied with a reservoir and a vertical turbine pump. Based on hydraulic calculations of the sprinkler systems, the system futhest from the water supply has a system demand of 520 gpm @ 125 psi. A system closer to the water supply has a system demand of 688 gpm @ 105 psi. Both systems are ordinary hazard occupancy with a water supply duration of 60 minutes. In order to size the reservoir and pump system is it a matter of sizing the reservoir to meet the demand of the 688 gpm system (i.e. 41,280 gal.) and then size the pump to meet the pressure requirements of the 520 gpm system ?





RE: Reservoir Size for Sprinkler System
I offer one caveat and that is it has been a long time since I looked at vertical shaft pump supplied from a reservoir so you will want to confirm my statement regarding the pump capacity at 140% of its discharge pressure.
RE: Reservoir Size for Sprinkler System
The reservoir should be large enough to meet the highest flow rate PLUS the hose stream (probably 500 gpm in your example) for 60 minutes. Looks like a 75,000 gallon reservoir is in order, but remember 75,000 gallons must be available to the fire pump at all times. You might need to take into account the volume of water which is too low for the pump to access and you may need to consider evaporation or arrange for an automatic fill to ensure the reservoir level is maintained above the calculated minimum.
RE: Reservoir Size for Sprinkler System
The reservoir is sized to supply the greatest demand of flow. This would be the 688 gpm area. As long as the reservoir does not supply hydrants or hose valves, you should not need to add the hose allowance. (11.1.5.3 Where pumps taking suction from a private fire service main supply sprinklers only, the pump need not be sized to accommodate inside and outside hose. Such hose allowance shall be considered in evaluating the available water supplies. ) Therefore, you are probably looking at +/- 45k gallon tank.
Good luck with the project.
Travis Mack
MFP Design, LLC