Corrected entry: After Ben Affleck sets off the sprinklers and drenches the office, none of the computers or monitors seem to short out despite being deluged with water.
Corrected entry: When Affleck sets off the sprinkler system in his firm's building he does it by holding fire to one of the sprinklers. Sprinklers are set off by heat melting the water stopper in the sprinkler. What Affleck did would have set off one sprinkler, not the whole system.
Correction: Most sprinkler systems are kept pressured. When a single sprinkler goes off the pressure drops, this is detected and the sprinkler pumps are activated. This supplies enough pressure to burst the other sprinkler heads. Secondly, the sprinkler head in the film had a glass/alcohol stopper - when the alcohol is heated it expands, breaking the glass.
When the sprinkler head goes off flow sensors are triggered, not pressure sensors. The flow sensor triggers the fire alarm, maybe a booster pump that maintains flow not pressure. Sprinkler heads are not triggered by pressure. The system will have hookups for fire department to connect the fire engine pumps to also boost flow.
Correction: Fire sprinkler systems cut power on activation to electrical supplies in buildings.