Initiating Devices: Manual Pull Stations and Waterflow Switches

This article provides an overview of manual pull stations and waterflow switches, which are both fire alarm initiating devices. We'll explain what they are, how they work and where they are used. In commercial fire alarm systems, initiating devices play a critical role of detecting an active fire and dangerous level of carbon monoxide as well as monitoring the sprinkler system to ensure that it's in proper working condition.

Manual pull stations are wall-mounted devices that are located near the exit doors to allow the passersby to manually trigger a fire alarm. Manual pull stations come in two types: Single Action and Double Action. Single Action pull stations require only one hand motion, such as pulling out or pushing down a lever, to trigger the alarm. Double Action pull stations require two hand motions, such as lift-up-and-pull-down or push-in-and-pull-down, to trigger the alarm. But that’s not all. Sometimes a protective plastic cover is added to a Double Action pull station, making it a Triple Action manual pull station.

You may be wondering why anyone would install Double or Triple Action pull stations when Single Action pull stations seem far simpler to use. Turns out a major problem with Single Action manual pull stations is exactly that — it’s far too easy to trigger an alarm. An accidental touching or leaning, or a child who is in a mischievous mood, can easily trigger a false alarm. If a pull station is located in a high-trafficked area where a false alarm is a regular occurrence, we recommend a Triple Action pull station that has an added local sounder that activates when the protective plastic cover is lifted in order to deter malicious acts.

Waterflow switches are devices that are mounted on the primary and secondary water pipes that supply pressurized water to the sprinkler heads, and are used to detect water movement in the sprinkler pipes. When the ambient temperature around a sprinkler head reaches the set threshold (typically 135°F or 170°F), it will begin discharging water to extinguish the fire, which triggers water to flow through the sprinkler pipes. Waterflow switches have a paddle that’s inserted into the pipe and moves in the direction of the water flow. When any water movement is detected, waterflow switches transmit an alarm signal to the Fire Alarm Control Panel (FACP) to notify the occupants to evacuate.

To learn more about different fire alarm initiating devices, read these related articles:

Initiating Devices (Part 1) - Smoke Detectors, Duct Smoke Detectors and Beam Detectors

Initiating Devices (Part 2) - Heat Detectors, CO Detectors and Multi-Sensor Detectors

Initiating Devices (Part 4) - Supervisory Switches for Monitoring Automatic Fire Sprinkler Systems

Are you looking for a new fire alarm system for your commercial space? Or need to upgrade an existing one? Download this FREE eBook that explains different fire system components.

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