You're already familiar with the inspector's test as a required component of a sprinkler system, but today we're diving into the true purpose and details behind this important aspect of a sprinkler system.
The purpose of the Inspector's Test can include: providing the ability to (1) test the sprinkler system's alarm/waterflow device, (2) test the opening of a dry-pipe or pre-action valve (for dry-pipe or pre-action systems systems, of course), (3) test the trip time from when the valve is opened to the arrival of water, where necessary, and (4) can aid in venting trapped air.
The inspector's test can be coupled as an air vent for a wet system or an auxiliary drain, although we'll explore those components in more detail separately.
Discharge: Used to discharge water during the test or draining of the system. Discharge must:
Drum Drip: Provided for dry or pre-action systems to collect condensate within the system for purging. At a minimum they must be:
Orifice: The orifice (within a sight/site glass) simulates the flow of a single sprinkler in order to ensure that the sprinkler waterflow alarm will activate upon the flow of a single sprinkler. The orifice must:
Sight/Site Glass: typically provided where water discharge is not visible from the control valve (NFPA 13 2002 A.18.104.22.168, 2007-13 A.22.214.171.124, 2016 A.126.96.36.199). As a side note, I don't understand why Drive Thrus and Site Glasses are spelled the way they are, but I don't try to fight the system. Just know that common language often refers to these as 'site' glasses despite not actually referring to a large area of land.
Supply: The supply simply connects the most remote branchline from the riser to the inspector's test (for a remote inspector's test). It must:
When & Where Required: inspector's tests are required on each wet, dry, or pre-action sprinkler system:
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Joe Meyer, PE, is a Fire Protection Engineer out of St. Louis, Missouri who writes & develops resources for Fire Protection Professionals. See bio here: About