It does not necessarily come up often, but the volume of a fire sprinkler system does carry several requirements.
Dry and Preaction systems carry water delivery requirements, while all systems carry requirements for drainage. Today I'm summarizing requirements related to when volumes of fire sprinkler systems are important to consider.
Dry System Capacity
Systems under 500 gallons (1900 L):
Systems between 500 and 750 gallons (1900 - 2850 L):
Systems over 750 gallons (2850 L):
Hazard No. of Remote Sprinklers Initially Open Max. Time of Water Delivery
Dwelling Units 1 sprinkler 15 seconds
Light 1 sprinkler 60 seconds
Ordinary I 2 sprinklers 50 seconds
Ordinary II 2 sprinklers 50 seconds
Extra I 4 sprinklers 45 seconds
Extra II 4 sprinklers 45 seconds
High Piled 4 sprinklers 40 seconds
Note for Dwelling Units:
Dry systems must discharge water in 15 seconds, regardless of system size (NFPA 13 2002 220.127.116.11.1, 2007-2016 18.104.22.168).
Inspector's Tests are used to test water delivery times for dry systems when water delivery time test is required. See this article for details and components on inspector's test and drains.
Pre-Action System Capacity
Single-Interlock and Non-Interlock Systems:
Double-Interlock Systems of 500 gallons or less (1900 L):
Double-Interlock Systems over 500 gallons (1900 L):
Dry and Pre-Action System Drainage
Auxiliary Drain Location:
Trapped Sections less than 5 gallons (20 L):
Trapped Sections more than 5 gallons (20 L):
Wet System Drainage
Trapped sections of pipe less than 5 gallons (20 L):
One of the following is required (NFPA 13 2002 22.214.171.124.2.3, 2007-2016 126.96.36.199.2.3.):
Trapped Sections between 5 and 50 gallons (20 - 200 L):
Trapped Sections 50 gallons (200 L) or more:
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.