Your building’s fire protection system is essentially fire sprinklers, pipes, and valves. During a fire emergency, the sprinkler responds to the rapid rise in temperature and, aided by open valves, allows water to flow freely through the pipes towards the fire. When combined with enough water, these three fire safety components can save lives and thousands of dollars in avoided property damage. But while sprinklers are nearly fail-proof, the valves are particularly prone to the human element. Enter the tamper switch.

What exactly is a tamper switch? In this blog, we’ll dive into that question and describe three particular valves most commonly monitored by them. Near the end, we’ll describe the different tamper switches used to monitor those valves, a sneak peek of which is demonstrated in the table below:

Three Most Common Fire Protection Tamper Switches
Tamper Switch for Butterfly Valves and Post Indicator Valves by System Sensor Tamper Switch for OS&Y Valves by System Sensor Tamper Switch PSP1 Plug-In Special Purpose Supervisory Switch by System Sensor
Butterfly and Post Indicator Valve Tamper Switch OS&Y Valve Tamper Switch Plug-In Special Purpose Tamper Switch

We must start with an important warning: removing, replacing, or otherwise tampering with a fire protection tamper switch can render them ineffective and should only be carried out by a qualified professional. It’s always better safe than sorry. With the disclaimer out of the way, let’s proceed.

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A tamper switch is a mechanical and electrical device connected to a fire protection valve that signals a warning if the valve partially or fully closes. Regardless of the type of tamper switch, they all function similarly. The tamper switch features an actuating unit, usually a lever or cable with a resting position. When the valve closes, the actuating unit breaks an electrical circuit which triggers a signal. Think of it like a light bulb: when the light switch is on, a circuit is formed and the bulb shines brightly. When the switch is turned off – or, in the case of a fire protection tamper switch, the valve closes – the circuit is broken. For tamper switches, this broken circuit creates a signal. In most jurisdictions, this does not mean the fire alarm goes off (though check with your Authority Having Jurisdiction (AHJ) to make sure of your local rules) but rather the tamper switch sends the signal to a fire control panel which creates a record of the incident.

As implied earlier, a tamper switch is a crucial add-on because the fire protection system only works if an ample water supply is available. Therefore, knowing the status of the various valves in the system can mean the difference between a functioning fire sprinkler system, or this…

Building fire in Chicago

Building fire in Chicago (image credit)

As I’m sure you can imagine, there are both malicious and unintentional reasons for a closed valve. Before burning a building, the first thing a savvy arsonist will do is shut off the water supply to the sprinkler system. With a tamper switch, this change of status alerts the building owner through the control panel.

System maintenance is a more common reason for a closed valve. If the system needs de-activation to change a component (such as replacing a fire sprinkler head), the valve(s) will be turned off, triggering the tamper switch to signal an event. This trigger creates an instrumental record for facilities maintenance or the sprinkler contractor to reference as a means of ensuring they're reopened before the job is complete.

A Fire Control Panel

A Fire Control Panel (image credit)

There are many makes and models of tamper switches available. Let's highlight three primary types:

  • Outside Screw and Yok (OS&Y) Gate Valve Tamper Switch
  • Butterfly Valve or Post Indicator Valve Tamper Switch
  • Special Purpose Plug-In Tamper Switch

The OS&Y Valve is usually the first valve in a fire protection system. Consider it the gateway between the main water lines running through your town and your building’s fire protection system. You can learn more about them here. The important thing to note for our purposes is the valve must be open – which is visually identifiable because the screw or stem sticks up out of the top of the valve – for the building to have a charged sprinkler system. If someone closes this valve, the building’s fire protection system is nothing more than an expensive accessory. Therefore, it is crucial that the valve remains open. The OS&Y tamper switch provides added peace-of-mind by monitoring the valve’s status.

OS&Y Valve with Tamper Switch Installed

OS&Y Valve with Tamper Switch Installed (image credit)

The next tamper switch works for two different types of valves. The first is a very common valve in most modern sprinkler systems called a butterfly valve, named after the way the valve’s gate turns on a vertical axis instead of a moving up and down. The butterfly valve is used to shut off the water supply at various points throughout the system and like the OS&Y valve, a closed butterfly valve means an area of the system is not ready for action. The tamper switch is on the lookout for a closing butterfly valve and signals the control panel when it happens.

A post indicator valve’s gate is located underground, at the bottom of the stem (or post) in the image below. Similar to an OS&Y valve’s raised screw, the post indicator offers a visual ‘OPEN’ sign identifying the status of the underground gate valve. But since monitoring the ‘OPEN’ sign 24/7 is unrealistic, a tamper switch is added as a fail-safe.

Post Indicator Valve

Post Indicator Valve

Finally, a Special Purpose Supervisory Switch is used when no other tamper switch will do. This switch features an electric cable wrapped around the valve’s stem or handle and plugged into an inlet on the tamper switch. When the handle turns, the cable dislodges from its plug, breaking the circuit and sending a signal to the control panel.

To revisit the table from the beginning of this blog (which is replicated below), you now know the difference between the three models. QRFS proudly offers System Sensor tamper switches. System Sensor has been around forever and makes an excellent tamper switch. They feature weather resistant bodies for indoor or outdoor mounting, tamper-resistant screws with a special key to stop the housing from being opened unintentionally, and a single conduit entrance for easy installation. At QRFS, we have all three models in stock and will have them in your hands fast.

Click any of the products below to get started.

System Sensor® Fire Protection Tamper Switches from QRFS:
Tamper Switch for Butterfly Valves and Post Indicator Valves by System Sensor Tamper Switch for OS&Y Valves by System Sensor Tamper Switch PSP1 Plug-In Special Purpose Supervisory Switch by System Sensor
Tamper Switch for Butterfly Valves and Post Indicator Valves by System Sensor Tamper Switch for OS&Y Valves by System Sensor Tamper Switch PSP1 Plug-In Special Purpose Supervisory Switch by System Sensor
Shop for Tamper Switches Shop for Tamper Switches Shop for Tamper Switches

This blog originally posted at by Jason Hugo on February 19, 2016. If you like our informative content, see the rest of our blogs by visiting Thoughts on Fire or connect with us on Facebook or Twitter