Telepathic Sprinklers

When someone needs to create chaos in a building or just get everyone to leave, they trip the sprinkler system. Just apply a lighter flame, or perhaps a bullet, to one fire sprinkler, and all of the sprinklers on that floor—or even in the entire building - will suddenly kick off. Everyone gets drenched, and there's a mass exodus from the building.

The only problem with this is that sprinklers do not work that way. Practically all sprinkler systems are of the "wet pipe" type, where the pipe to all of the sprinklers is full of water under pressure, and the only thing stopping it coming out is a heat-sensitive valve in the sprinkler head. Heat it up enough, and the valve pops—out comes the water.

But only from that single sprinkler head. There's no communication between the sprinklers. One of them going off will not trip any of the others. You might have thought that maybe it was some sort of water-pressure shock system, but no; ordinary fire sprinklers are entirely independent. And smoke detectors and fire alarm pull stations are almost never set to trip sprinkler systems. Sprinklers will set off the alarm, but not vice versa.

This is perfectly sensible, of course. If all of the sprinklers went off at once then it might reduce the spread of the fire a little more than if only sprinklers in hot areas tripped, but at the price of water-damaging a lot more of the building than was actually necessary. And all sprinklers going off at once would considerably reduce the water pressure available to each one, reducing the fire suppression in the area that's actually burning.

Of course, if the sprinklers really were linked, annoying heroes, villains and mischievous children could set 'em all off whenever they wanted.

There are "deluge" systems, in which the sprinklers have no valves of their own and a "deluge valve" lets water into the pipes that serve them all. These are used only for places that contain major fire risks, not regular warehouses or factories.

This trope is so prevalent in the media that people now expect sprinklers to go off all at once. Businesses are reluctant to install sprinkler systems because they think even the smallest fire will cause enormous water damage. This trope may also have been responsible for a lot of real-life criminals drenching their—and only their—jail cell.

Also, while sprinklers in media spray little bits of clear water, a real sprinkler system - which typically sits for years without use and which is designed to put out or stop the spread of fires as fast as possible - dumps between twenty and one hundred gallons (80-400 liters) of filthy, stagnant water per sprinkler per minute. Not exactly the best way to spend your day. Compare that to a simple shower, which puts out about one-and-a-half to two gallons (six to eight liters) per minute.

Telepathic Sprinklers is a subtrope of Did Not Do the Research and Reality Is Unrealistic.

Examples of Telepathic Sprinklers include:

Anime and Manga

Touma utilizes this trope in the second episode of A Certain Magical Index. His opponent has magical wards set up all over his apartment building, and he needs to destroy them to make the man beatable. Setting off the Telepathic Sprinklers (which cause the ink on the wards to run, making them powerless) disables all of the wards at once without him needing to track them all down.

Film

Averted in Aliens, Ripley holds a lighter to a sprinkler in the med-lab to attract the attention of the Marines in the control room, and it doesn't activate any of the sprinklers outside that room.
Done in The Matrix, shortly after the famous lobby scene. Neo's elevator firebomb somehow manages to set off every sprinkler in the building, drenching the Agents (several stories above the blast) at a dramatically opportune moment. Somehow the dinky sprinklers in the room also manage to fill the place up with what looks like about a foot of standing water, just to make the upcoming helicopter/machine gun scene look that much more badass.
In Casino Royale (2006), Bond is chasing a bomber through Miami International Airport when the bomber changes into a TSA uniform and turns a "sprinkler activation" key on an alarm panel, drenching the terminal.
- Just starting a regular fire alarm would have worked exactly the same way and there was no reason at all to drench the whole place in water. It just looks more interesting than dry people leaving the building in an orderly fashion.
- Possibly justified in-universe by 007's sense of humour.
In The Incredibles, Bob gets a message that self-destructs, causing a small fire for a brief second that sets off all the sprinklers in the house, getting groans from the rest of his family. Cut to them drying books and furniture to avoid permanent water damage. Them having fire sprinklers in a residential house seems odd in and of itself, especially since they had no clue at that time that their baby had fire powers. It works because of the Rule of Funny.
In Meet the Robinsons, Lewis' invention at the science fair, after being tampered with, sets off a chain of events that makes... a scale representation of Vesuvius explode, setting off all the sprinklers in the gym.
In the movie Constantine, the title character does this, after having his assistant bless the water. Enter pissed-off smoking demon hordes.
In Bruce Almighty, Bruce uses the power of God to stop a party by activating the house's sprinkler system. Justified in that the sprinklers are being set off by willful divine intervention, not a fire.
In Mean Girls the headmaster stops a riot by setting off a single fire alarm and drenching everyone. This was particularly effective as 'everyone' was teenage girls who were worried about their hair. However, the sprinklers appeared to only come on in the corridor, not the rest of the school.
In Frequency, Dennis Quaid's character does this to not attract attention to himself, when he escapes his interrogation room after electrocuting the villain who has framed him for murders he didn't commit.
In the movie Accepted during the big party scene, one of The Rival school members pulls the fire alarm. For some reason instead of releasing a siren and alerting the fire department, all this does is turn on the sprinkler systems and causes everyone to start dancing in the rain.

Wet T-shirt party!

In Hackers, the entire sprinkler system is computer-controlled and can be set to 'test' at a certain time.

Literature

Averted in the Dresden Files novel Small Favor. Harry sets off most, if not all, of the sprinklers in a building by sending the heat from a fire spell to each individual sprinkler. And it's mentioned that the stagnant water stinks.
Happens when a character in Joan Hess's A Conventional Corpse sets off the fire alarm at a college, and the sprinkler system goes off on every single floor of the building. Particularly conspicuous, as colleges would be the last place to want Telepathic Sprinklers even if they did exist, due to student-prank false alarms.

Live Action TV

House:
- Amber "Cutthroat Bitch" Volakis attempts this by blowing smoke from a cigarette on a sprinkler, in an attempt to drench Dr. Cuddy with the intention of getting her thong. It doesn't work. So she uses the lighter directly, and sure enough the sprinklers in the entire sector go off.
- And again, in episode 6.12 (Moving the Chains), when the mystery prankster sets off a fire alarm in House and Wilson's apartment, causing every sprinkler in the place to let loose.
- And in episode 4.2 (The Right Stuff) not so much a telepathic but more a hesitant sprinkler. Using the defibrillator in a hyperbaric chamber causes a small fire. The fire alarm is instantly triggered, and the staff quickly puts the fire out. It is not until 10 seconds later that the sprinkler kicks in, apparently for no other reason than the Rule of Funny.
In Law and Order: Criminal Intent episode 2.6 (Malignant) one half of a pharmacy had suffered water damage due to the sprinklers going off. The other half did not get wet because the pharmacist had disconnected that half of the system. The otherwise savvy detective Goran does not comment that this was unnecessary.
Frasier
- Crane, in the episode Liar Liar, set off a sprinkler to interrupt a romantic moment between two people. Justified, since he was in the same room, behind a screen. Watching him emerge, soaking wet, a triumphant smile on his face? One of the funniest moments in the show. Granted, that instance seemed to only apply in regards to the apartment room, as the hallway oddly didn't seem to any water being sprayed.
- There was another episode where he tried to empty out a theater by setting off the sprinklers. All he accomplishes is giving himself a shower, because only the one sprinkler is set off.
- However in the episode where the brothers open a restaurant, a Cherries Jubilee explosion at a customer's table caused all the sprinklers to go off, even the ones in the kitchen.
In one Halloween episode of Roseanne, she sets off the sprinklers at the lodge with a lighter as her big Halloween prank. She stands on a chair with an umbrella as the rest of the party goers are soaked.
The second season finale of Community featured Troy rigging all of the sprinklers in the library to spray paint instead of water, which all go off at once when Shirley pulls the fire alarm.
Possibly averted in Due South, when Frasier and Vecchio are trapped in a bank vault. Frasier trips the sprinkler in order to flood the vault, and that sprinkler is the only one to go off in the whole bank.

Music

There was a music video, can't remember the song, where a bunch of partiers tripped the nightclub's sprinklers. Almost an aversion, since multiple people are tripping multiple sprinklers, but they were having way too much fun dancing under water that should be highly pressurized, filthy, and probably ice-cold.

Video Games

In No More Heroes a mook holds a torch up to a sprinkler, causing all the sprinklers in the hallway to go off. Travis's ~~lightsaber~~ beam katana isn't waterproof, so in results in a comedic electrocution, and a short detour to turn off the sprinklers.
The 'massive flood of sprinklers' variant is subverted in Grim Fandango, when the protagonist tries to flood a vault this way to escape. It just results in a puddle and a subtle, but very useful, clue.
The player has to make use of this in Space Quest 2, with the classic 'wastebasket full of paper' method.
Averted in The Sims 2 (and probably the other two, but I can't speak for those). Chances are, you're only going to have one sprinkler in the house to begin with, in the kitchen, where there's more danger of fire; but if you do have more than one (likely by the fireplace or the grill if it's covered), only the one in a position to put out the fire goes off. And really annoying in the college expansion when that asshole cow decides to be funny and set it off.

Web Comics

The Last Days of Foxhound:
- Decoy Octopus blows cigarette smoke at the hospital room sprinklers and sets all of them off, much to the chagrin of the injured Mantis and Ocelot.
- And this:

Sniper Wolf(With a partially unzipped jacket): Oooh Mantiiiis!
Psycho Mantis: * Looks to the left* Eeh?
Next Panel. Sprinklers are going off.
Liquid Snake: Oh great. that's just what I need.

In an early arc of El Goonish Shive, Tedd and Elliot attempt to invoke this to stop the Goo Monster. It doesn't even work at all, because the school skimped on the sprinkler systems in order to buy more murals.