Firefighting Simulator - The Squad

Hoses no matter the type (i.e attack lines or nozzles from the Viper/T-Rex) will put out approximately 3400 liters per hour with continuous use. Meaning this achievement will take around 30 hours to unlock if playing solo.

However, if you play in multiplayer the progress is shared amongst all players. If you play this way you can significantly cut down the grind. The times to unlock this achievement depending on the number of players you have are as follows:

1 Player - 30 hours
2 Players - 15 hours
3 Players - 10 hours
4 Players - 7.5 hours

There does not appear to be an idle kick either, so you can simply rubberband/tape down and let the game run on its own, allowing you to step away and do other things. Though be warned progress is not saved until the successful completion of the mission, therefore if your game crashes or a player disconnects, progress will be lost. I would recommend only going a couple hours at a time or whatever time frame you're comfortable with for that reason.

To add some extra information onto KawiNinjaRider7 Guide. If you head into Settings, under Gameplay, You'll see an option called "Toggle Quench Input" I recommend turning this on, This will allow you to press RT once and it will keep spraying water for you without having to hold RT or place anything onto it to keep the button down. Hope this helps alittle extra.