A safety officer argues: 'Fitting a second water tank on the roof of the warehouse will let the sprinklers run for twice as long as they can run now, and so give the fire service twice as much time to reach us.' Which of the following, if it turned out to be FALSE, would most damage the officer's argument?

The doubling rests entirely on the roof tanks being what limits the running time. If the sprinklers are also fed from a mains connection or an underground sump, the running time is set by that supply and adding a second roof tank need not extend it at all. The maker of the tank, the fire service's knowledge of the road and a recent inspection could each be false without disturbing the reasoning.