Pre-action Systems Sensors in the area of the fire are activated. The water valve is then open. And water flows to the area.
Deluge System All sprinklers are activated at once when a detecting device is activated.
Typical Wet Pipe System In a typical wet pipe system, water enters the building at a determined pressure.
Backflow Preventers Backflow preventers are placed before the riser. If there are significant decreases in water pressure, the backflow preventers prevent water from being sucked out of the sprinkler system. These backflow preventers must be checked by certified plumbers at least annually (EPA requirements).
Main Water Clapper The water then enters the main section of the riser. There is a main water clapper that sits at the base of the riser. If there is major water pressure loss, the water will stay in the sprinkler system.
Water Gauges Water pressure gauges are found above and below the water clapper. This will alert the person to pressure problems in the water lines. In a wet pipe system, both pressure gauges may read the same. Check the design spcifications!!
Water Flow Alarm These are found above the main clapper. If there is a flow of water, the alarms will be activated.
2" Main Drain A two inch pipe comes out of the main riser area to a drain. This two inch line is used for testing purposes. Closing the water valve above the 2 inch line then opening the 2 inch water line tests water coming in from the municipal service.
Riser The next section of pipe is the riser pipe itself. The riser pipe goes up to the sprinkler branch lines in the building.
Branch Lines The branch lines are typically smaller than the riser. This decrease in the diameter of the branch lines increase the pressure in the lines.
Inspectors Test Located at the furthest point from the riser Simulates the opening of one sprinkler head
Wet Pipe Sprinkler System Inspections Inspector's test 2 inch main drain test Water flow alarm test
Inspectors Test Signifies that one sprinkler head at the sprinkler head furthest from the riser has been opened. This verifies that adequate pressure and flow can be achieved.
Water Flow Alarm "Trip test“. –At the inspector's test valve, open the inspectors test valve. –A slight decrease in pressure should be observed. –The water flow alarm should be activated and the fire department should receive a signal that the fire alarm has been activated. –There should be a short time delay from when the water flows and the alarm is activated. –The delay should not be any greater than 90 seconds. –Close the inspectors valve and reset the system.
Two Inch Main Drain Test –The purpose of the two inch drain is to determine if there is adequate water supply to the system. –Open the two inch drain fully, check and record the water pressure. –There should not be a significant drop in water pressure when the two inch drain is open. –If there is, there may be a blockage in the supply line. –Close the two inch drain and record the pressures. –The pressure should return to approximately normal.