My question is about sizing fire protection tank (the tank would be expected to contain enough water to extinguish a fire without any inflow into the tank, as in the event of a municipal supply interruption). My question is: do you size the tank for the higher demand between the hydrants and sprinklers, or for the total demand of the hydrants and sprinklers combined. For example, if my hydrant demand is 150 m3/h, and my sprinkler demand is 100 m3/h, and I need to store the water for 3 hours, then do I size the tank as per option 1 or 2 below:
- Option 1: 150 m3/h for 3 h (450 m3 tank)
- Option 2: 250 m3h for 3 h (750 m3 tank)
Is there a rule in the NFPA standards, or is one expected to make a reasoned judgement on whether the sprinklers and hydrants would need to be used simultaneously during a fire hazard?