Sprinkler pumping out fresh clean water

This is how sprinklers typically are shown in movies. They show the sprinklers pumping out water that is fresh and clean. In reality, the water from fire sprinklers is often very dirty.

Yes, normally in movies the sprinklers look clean, but in a building, the water has often been sitting in the sprinkler pipes for quite a long time, and the water gets dirty.

Mhm, not to mention the age-old Hollywood myth of every sprinkler in a building discharging, even though that’s a deluge system which are only used in high-hazard applications (AKA not your typical public building).

Sprinkler systems have water that is stored in the sprinkler pipes for a long time. Like decades in the pipes.

The reason for this is that in case the building’s water is not working, the fire sprinklers will still work if there is a fire.

Wet systems at least: dry, pre-action, & deluge systems likely have cleaner water as the sprinkler pipes only fill with water when a sprinkler head bursts (or a detection system primes the pipes in the case of pre-action & deluge systems). Wet systems have the quickest response time given there’s water right at each sprinkler that’s available immediately if one should burst, but in all likelyhood that water won’t last long if the building’s water supply is down.

Do wet systems cut off the water pump when all of the pipes are pressurized? If not, what do they do? It’s a bit off topic, but I’ve always wondered this

I’m not sure but it wouldn’t surprise me if the pipes are always pressurized, just like how pipes connected to faucets never burst despite the faucets blocking the flow (I also don’t think sprinkler systems usually have their own pumps since normal building water pressure should be enough in most cases). A waterflow switch would have to be installed for flow detection too, adding cost to the system.