Pipe Layout

• The sprinkler system starts with a pipe leading directly up from your house's water supply (located in the basement) to the ceiling of your top floor. This vertical pipe is called the "riser." You will have to cut 2-inch-wide holes in the horizontal wooden beams behind your walls (between the studs) in order to fit the riser. At the top of the riser, install an elbow fitting and attach it to a pipe that runs above the rooms. Put a sealed cap at the end of this horizontal pipe.
  If your house has more than one floor, install a T fitting along the riser just above the ceiling of the first floor. Next, install a horizontal pipe into the T fitting running above all the rooms. Cap this pipe as well.
  Finally, return to the basement and install a T fitting on the riser about 4 feet from the floor. Install a short, 2-foot long pipe into it but don't cap it.
  
  

Fixtures & Valves

• On the riser, below the first T fitting, install a pressure gauge, a rubber-faced check valve and a flow detector. Next, on the short pipe attached horizontally to the first T fitting, install a simple ball valve.
  Next, you need to install the sprinkler heads in each room. First, you must drill a hole in the long, horizontal ceiling pipe(s) directly above the planned head site. A thin metal pipe with threaded ends must be cut to the proper length, inserted and sealed in each hole. The sprinkler heads are then attached to each pipe.
  Finally, install an inspector test valve about 1 foot from the capped end of the horizontal ceiling pipe on the top floor.
  
  

Triggering Mechanism

• In the event of a fire, the sprinkler head shoots pressurized water from its connecting pipe onto a small horizontal plate, causing the water to spray around the entire room. The sprinkler head assembly consists of the pipe opening, the plate, two or three metal strips which secure the plate and a special piece of metal alloy fit snugly between the opening and the surface. Under normal conditions, the alloy piece forms a tight seal, keeping the water from leaking out of the pipe.
  However, this special metal used is part of a class of bismuth-tin alloys with melting points between 158 and 270 degrees F, depending on their exact composition.
  As the fire burns in the room, super-heated gas rises to the ceiling where it quickly melts the bismuth-tin alloy. With this stopper piece gone, the water is free to escape from the pipe and spray against the plate below.
  To stop the sprinkler, you have to shut off the main water line in the basement.