| A small residential fire sprinkler head outputs around 15gpm of water. While keeping a roof wet is different than wetting down a room on fire, a roof is big and you need to be sure it stays wet, so let's say you want to keep it wet with 30gpm. And lets say you have to keep it wet for 24 hours until the fire danger passes. That's around 40,000 gallons of water. Where are you going to get that water? You can't count on the local utility keeping pumps running. If you're lucky you have a well, but a good residential well would yield around 10gpm, and if you and your neighbors are all pulling out water at the max rate together for hours or days, it may run dry while you wait for water to percolate in. So you need a huge tank of water - a 50,000 gallon tank is around 35 feet in diameter and 7 feet high. Hope you have a big yard and lots of money, the tank alone will probably cost $30K. So figure around $50K to install the system. I hope you have a big back yard for it. That bunch of firefighters you want to get rid of help protect many square miles of land, putting that $50K sprinkler system on 10,000 homes would cost $500M - that's a lot of firefighters and equipment. I think there are better ways to keep your roof from burning, but even a metal roof is no guarantee that your house will survive a large wildfire unless you also keep the land devoid of fuel. And you could still fall victim to a piece of flying ember that happens to land on a vulnerable spot of your house. |