AnsweredAssumed Answered

Sprinkler water storage tank - include hose stream allowances, or not?

Question asked by joseph.keller on Oct 9, 2020
Latest reply on Oct 13, 2020 by faizal_sharin

A golf course clubhouse building is currently sprinkler protected.  The building is remote from any municipal water service and is served domestically by a small well.  The building fire sprinkler system derives water from an on-site pond water supply, with a vertical fire pump in a pit adjacent to the pond.  The water pond and fire pump in a pit are not a desirable operation and are not easily maintainable, and the fire water storage and service are in need of upgrade /replacement.


Description of the facility:  The building has an unheated basement (9600 SF) for parking and charging electric golf carts protected by a dry pipe sprinkler system.  The first second and third floor attic are protected with wet sprinkler system.  The first floor (9600 SF) has toilet, shower and locker rooms, a small retail pro shop, and a small food and snack kitchen area (450 SF) with a grill hood equipped with suppression system, along with some adjacent dining areas.  The second floor (9600 SF) has a larger kitchen (850 SF) with some hoods also equipped with suppression systems, and dividable catering hall rooms, and adjacent toilet rooms.   A third floor attic space (9600 SF) is unused but sprinkler protected. 


As a golf course club house, per NFPA -13, the building could be designed to be protected at mostly a Light Hazard occupancy, except for the 2 kitchen areas which are considered as Ordinary Hazard Group 1.


Light hazard general clubhouse areas will require 1500 SF at 0.10 GPM/SF density = 150 GPM.  Allowing for a 130% hydraulic demand factor yields a sprinkler demand of 195 GPM and at Light Hazard duration of 30 minutes, a minimum water storage tank (sprinkler flow only) capacity of 5850 Gallons is needed.


Ordinary Hazard Kitchen areas are not completely separated from dining room areas, so if we allow a most stringent case sprinkler design to calculate a maximum 1500 SF at a 0.15 GPM/ SF density = 225 GPM.   Allowing for a 130% hydraulic demand factor yields a sprinkler demand of 292.5 GPM and at Ordinary Hazard minimum duration of 60 minutes, a water storage tank (sprinkler flow only) capacity of 17,550 Gallons is needed.


The issue is at question is how to handle the hose stream allowance?  Is it required that the on-site sprinkler water storage tank include outside hose allowance i.e., the greater of either Light Hazard 100 GPM for 30 minutes = 3000 GPM; or the Ordinary Hazard hose allowance of 250 GPM for 60 minutes= 15,000 Gallons ?  Including these hose stream demands would yield much larger tanks of 8850 gallons and 32,550 Gallons respectively.


While it is clear under  NFPA-13 / 2016 edition section A. that a fire pump (taking suction from the tank) and supplying the sprinkler system only would not have to include the outside hose allowance it is not clear if the tank must include the extra storage? NFPA-13 in sections on Water Demand and Water Supplies A11. appear to conflict on whether the sprinkler system water storage tank must include a hose allowance. 


Does the outside hose stream water for fire department use have to be included in the sprinkler water tank storage or can they be asked to derive their fire-fighting water from suction drafting from the remaining on-site water pond?


Understanding the goal of the project is to increase the reliability of the fire sprinkler system and eliminate the sprinkler supply from pond water and fire pump in a pit.  If hose stream water is added to tank storage the project cost increases greatly and the likelihood of going ahead with the project diminishes.