Location of drains
There are multiple types of fire sprinkler drains. It all depends on the type of sprinkler system that’s installed. The main type of drains are the main drain (installed at the riser), the inspectors’ test drain (installed at the end of the system), and the auxiliary drain (installed to drain a low lying area of a sprinkler system).
The main drain is located at the fire sprinkler system riser. Its purpose is to discharge water outside and away from your building or to a connection that can manage the flow of the drain and also to measure the water pressure in the system.
For systems with discharge drain connections, the connections depend on the size of the riser. The amount of water flowing through the main drain is based on the size of the sprinkler system. NFPA code determines the size of the drain connection based on the size of the riser. All types of sprinkler systems (dry, wet, preaction, and deluge) have different methods of drainage, but with the same purpose. Main drains are required to be permanently marked with identification signs hung from the pipe below the valve for which they are listing.
The inspectors test drain, or test and drain valve, is traditionally located at the end of the sprinkler system. This drain helps facilitate flow testing and is typically used in multi-story buildings. If you’re in a multi-story building, you will probably have sectional valves in the stairwell on each floor with a test and drain assembly that would test the alarm switch on that sectional valve as well as drain the system if needed. The testing part of the drain is a preinstalled restricted orifice that would simulate a sprinkler head discharge. There is a certain position the handle of the valve would need to be in in to flow through this restricted orifice.
The auxiliary drain is located where the pipe changes direction. Its purpose is to prevent any water remaining in the system after discharge by allowing you to drain water from a “trapped” or low lying area of the system. Though in wet systems, the piping is already full, so no discharge is needed. On dry systems, these drains can be located in areas susceptible to freezing and help in drainage of the system. All sprinkler types require auxiliary drains if there is danger of trapped water. Like the main drain, these drains must also have permanent identification signs secured to the pipe and below the valve. Additional signage is also required near the control valve. This signage will indicate the number of auxiliary drains and location of each drain.