Because fire sprinkler systems protect a variety of buildings and property, many different types have been developed over the years. These include wet, dry, deluge, pre-action and foam. Each has its own unique set of characteristics that protect the specific building and property for which it was installed.
As we learned on the previous page, sprinkler heads are connected to a system of pipes in the walls or ceiling of a room. These pipes are composed of steel, copper or fire-resistant plastic. The most commonly used system in commercial buildings is a wet pipe system, which is composed of steel pipes that are always filled with water (hence, the term "wet"). The water in the pipes is under a moderate amount of pressure. When the sprinkler head is activated, the pressurized water in the pipes is immediately released, providing a faster reaction time than any other type of system.
The wet pipe system is also the simplest and most reliable, boasting cost savings for easy installation and low maintenance. However, wet pipe systems are not always the best choice. Since the pipes are always filled with water, they're not recommended for locations where the pipes might freeze or in residential environments where accidental leaks could be detrimental.
As you might have guessed, in a dry pipe system, the pipes are not filled with water -- they're actually filled with compressed air. When the sprinkler head is activated, a valve releases the compressed air through the sprinkler head. Once all of the air is released, the pressure in the pipe changes, allowing water to fill the system. Dry pipe systems have a slower reaction time (up to a minute delay). To make up for this, dry pipe systems release a larger amount of extremely pressurized water, which requires larger pipes (and a larger budget). And, while a leaky pipe in a dry pipe system doesn't pose a flooding threat, maintenance to the system is more complicated and costly. So, this type of system isn't recommended unless specific conditions -- an unheated warehouse in Canada, for example -- exist. Read on to learn about the different types of dry pipe systems available.