Dry Sprinklers are installed in areas subjected to low temperatures when water can freeze. Typical areas include underground parking garages and loading bays. All the sprinkler piping is filled with air other than the water supply and valve with is always in a heated room. When a sprinkler head is activated during a fire, the air in the dry pipe will escape thus reducing the pressure in the dry sprinkler valve. This allows the valve to open admitting water into the dry piping towards the activated sprinkler head.
Dry sprinkler systems require more maintenance and are more complex, especially when fitted with excellerators or exhausters, devices that speed up the water delivery on long piping runs. Unfortunately, many times this equipment is not serviced properly which can cause the system to "trip" during the winter months, then freezing in the pipe, or worse, not working when there is a fire condition.
Some may think that if the sprinkler fails to activate, there is still a fire alarm. The sprinkler is the sensing part of the fire alarm system, so if the sprinkler fails, so does the automatic detection of the fire alarm on the sprinklered floors.
In order to properly service a dry sprinkler system, the dry valves must be opened up so the valve can be cleaned and reset. If the large bolts or nuts securing the face-plate are painted without marks and the paint job is over a year old, your sprinkler system is not been serviced properly.
The section of pipe between the sprinkler valve and the fire department couplings is dry as it is separated from the rest of the system by a check-valve. This check-valve is often located just inside the outside wall of the building. This dry section must be hydrostatically tested once every fire years.
