# PD 53


A Fire Sprinkler System is an active fire protection measure which essentially constitutes of a water supply system. It provides appropriate pressure and flow rate to a water distribution piping system onto which fire sprinklers are well connected. These cost effective sprinkler systems have long been in use in large commercial buildings, factories, small building systems and homes.


Sprinklers are in use in the US since 1874 and were initially installed in factories where fires used to have devastating effects both on human lives and the properties. It is now mandatory for the buildings in the US which are 75 ft high (23 m) or above to have sprinklers installed in them. These are also mandatory in the basements or other areas where fighters cannot easily direct adequate hose streams on the fire.

Use of sprinklers now is mandated by Building Codes and Bylaws, and also by Insurance Companies to minimize the chances of devastating fire tragedies that may result in substantial loss of lives and property. Building Codes in the US mandate the use of sprinklers in the places where more than 100 persons can assemble and also in overnight sleeping accommodations like hospitals, hotels, dormitories, nursing homes etc. Even local building codes in the US make the use of sprinklers necessary to receive funding from the state government or the federal government, or to receive certifications. These sprinklers are a must for the institutions where training programs for the medical staff are conducted.

Since 2011, Pennsylvania and California have made the use of sprinklers mandatory in all new residential constructions. These are the first two states in the US to do so.

Each Closed Head Sprinkler is held closed by making use of either a two-part metal link held together with a fusible alloy or a heat sensitive bulb. The link or the glass bulb exerts pressure on a pip cap which functions as a plug to stop the flow of water until ambient temperature around the sprinkler reaches to that of the design activation temperature of the individual sprinkler head. In a standard wet-pipe sprinkler system, each sprinkler gets activated independently as soon as the pre-determined heat level is reached. Because of this arrangement, only the sprinklers that are closest to the fire are activated and hence they can sprinkle water on the fire with maximum water pressure possible.

A sprinkler activation system typically does less damage to the property and makes comparatively less use of water than that of a fire department’s stream, which discharges water at the rate of 900 liters / min or 250 US gallons per minute. On the other hand, a typical industrial sprinkler discharges only 75-100 liters of water per minute, or 20-20 US gallons/ min. However, a typical Early Suggestion Fast Response (ESPR) sprinkler discharges approx. 100 US gallons/min or (0.0063 m3/s) at a pressure of 50 psi (340 kPa). Moreover, a sprinkler gets activated typically between 1 to 4 minutes while fire department’s vehicle usually takes around 5 minutes time to reach the spot and then another 10 minutes time to set up the equipment to apply water stream on the fire. This extra time may result in larger fire, requiring more use of water, besides causing more loss to the life and property.