Can you cause a sprinkler to leak by knocking it? Yes! Absolutely, you can. That being said, you could make your radiator leak by knocking one of the pipes. A properly designed sprinkler system should feature enough safeguards from accidental discharge being an issue.
The kind of risk involved depends on the kind of system that you’re working with. In the UK, there are three main kinds of system to consider:
- Deluge;
- Commercial; and
- Residential
In order to consider the risks and protections, we need to first consider the system type.
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Why use different sprinkler types?
Different fires need to be treated in different ways. Fires differ and so do the response strategies. Some strategies will prioritise the sprinkler strategy to minimise property damage (relying on other resources for evacuation), while others will use them to prioritise life protection. Other factors can include the kind of material contained within the facility, its use case, and who the occupants will be.
In the UK, the following standards are typically used, although other facilities may have had their own approved by the authority having jurisdiction:
- BS 9251: 2021;
- BS EN 16925: 2019;
- BS EN 12845: 2015;
- BS 8458: 2015; and
- NFPA 15
The different standards are also intended to reflect the different practices which take place in the construction of the different building types. Residential developments, for example, have substantially smaller void spaces than commercial and industrial properties.
Deluge
Deluge systems are the kind that you tend to see in films. They’re as different from the kind of systems used for homes and retail units as cats are from dogs. Deluge systems are used for special risk applications, such as fuel plants or (as seen in James Bond – Casino Royal) aviation facilities.
Unlike traditional sprinklers, deluge systems are designed to be triggered using electrical devices such as cameras and flame sensors. This is because deluge systems are designed so that all of the sprinkler heads discharge at once.
Due to the electrical trigger used in deluge systems, knocking the heads won’t cause them to discharge. There is nothing to dislodge in that sense. However, the pipes themselves could be caused to burst if hit with enough force. This would be a considerable amount of force though. Deluge systems use steel pipe and so we would be looking at them being run into by a HGV before there was any immediate risk of a burst.
Regardless, these pipes will typically be installed underground or in void spaces until they reach their areas of operation. Proper co-ordination at the design stage should ensure that the pipework itself is properly shielded within impinging upon protection or access to the areas themselves for their day to day use.
Commercial systems – storage areas
Commercial systems are considered to be a form of traditional sprinklers and are typically installed under BS EN 12845 in the UK. The system is activated using the head itself, which will contain either a glass bulb or fusible link, as shown below. The following image is credited to Warren Forensics: Know a Fire Sprinkler, Like a Boss – Part 1 | Warren Forensics
These blubs and links are designed to give way when exposed to a nearby fire. This ensure two things:
- The head is triggered primarily by heat;
- Only the heads near to the fire are activated
Glass is naturally more fragile than metal, but it also costs more. A good designer will factor this into their system. Commercial systems are the most likely to be knocked and so solutions designed to minimise accidental discharge in commercial systems are available.
The highest risk for knocking is in warehouse racking, as shown below, courtesy of mecalux.co.uk:
Warehouses with pallet racking like this often need heads installing along the shelving itself. Although a good designer will install the piping and heads in concealed spaces to avoid impacts from forklift trucks, it’s inevitable that, at some point, an item is going to fall from a shelf. Falling items can lead to accidental discharge. The best way to avoid this is to avoid in rack protection altogether. This can sometimes be done through the use of ESFR (Early Suppression, Fast Response) protection. Where ESFR is not found to be suitable, heads should be protected using guards, such as the Rapidrop option shown below.
In some cases, a pre-action system may also add additional protection against accidental discharge following impact. A pre-action system works by using the traditional mechanical triggers alongside electrical triggers, such as a heat detector or alarm. Systems using pre-action safeguards need both the mechanical and electrical triggers activating before a discharge takes place. A system may be kept dry until activated.
So, if a head is knocked, no water will be in the pipes because the electrical trigger hasn’t activated. Equally, if the electrical trigger has a fault, the pipes would fill but there would be no discharge without the mechanical trigger also being activated.
Importantly, pre-action systems aren’t suitable for all applications. There is a delay between the electrical trigger being activated and the water reaching the fire zone from the valve.
Residential systems and lower hazard commercial areas
Residential and commercial sprinklers are typically both traditional sprinkler systems. Residential systems are typically installed under BS 9251: 2021, while commercial systems are installed under BS EN 12845.
Areas such as these benefit from generally being able to conceal both the heads and the pipes in either the ceilings or the walls. This has both aesthetic and safeguarding benefits against accidental discharge. Our proposals provide examples of the kind of heads that we use and one of the images used is detailed below.
Figure 1 shows a sprinkler, concealed by a cover plate. Sprinklers installed like this are recessed into the ceiling void. A cover plate is then placed flush with the ceiling.
Considering this, it can be seen that before there would be a notable risk of accidental discharge following a knock:
- The cover plate would need to drop, which would then land on the floor directly below;
- The head would need to lower from the ceiling;
- A person would need to ignore the cover plate on the floor and the newly lowered sprinkler head;
- That person would then need to somehow knock a sprinkler installed a ceiling height with enough force to shatter the glass.
While stranger things have happened, it can be seen that the risk associated with accidental discharge from sprinkler heads which have been installed in this way is negligible.
What about mist?
One of the biggest selling points for mist is its ability to put out a fire without soaking the fuel. It’s important not to confuse this benefit with a view that mist systems don’t pose the same risk through accidental discharge. While the mist spray itself is less dense, the systems themselves often contain the same amount of water. There’s a myth that residential mist systems don’t need tanks. We actually run a CPD on this because these systems are often being mis-sold.
Even low flow, high pressure mist systems often require tanks. With some of these systems even needing larger tanks than the equivalent sprinkler system. This is due to the differences in the way in which the two systems work. Traditional sprinklers soak the fuel, cool the fire, and displace the air. Mist only cools the fire and displaces the air.
These differences lead to traditional sprinklers being able to limit their head count to no more than two heads operating (in a typical dwelling). On the other hand, mist systems require all nozzles within a compartment (or room) to operate up to a floor area of 64m2. If you’ve been ‘guaranteed’ a system that will work on 12 LPM, it’s crucial that you get that value verified by a second opinion from an accredited installer. We have some information on third party accreditation. The image below is an extract from the residential mist standard (BS 8458), which details the requirement for all nozzles to operate and for water supplies to be sized accordingly.
As a result, mist offers no more protection against accidental discharge than sprinklers do. Should a nozzle or pipe be dislodged, they contain similar (sometimes greater) water levels than traditional sprinklers. While mist systems may not soak the fuel in the event of a fire, an unfortunate knock could lead to the same outcome.
Is accidental discharge a concern for occupants?
It can be seen from the above that a properly designed fire suppression system, particularly in a residential setting, poses no greater risk from accidental discharge than your central heating system. In other settings, there are a large number of safeguards available which can also keep the risk minimal.
If accidental discharge is a particular concern for you, then please contact us for detailed advice and a break down of your options.
What should you do if your sprinklers do accidentally discharge?
If your sprinklers do accidentally discharge, we recommend taking the following actions:
- If you purchased your system with a shutgun, put this into position;
- Contact your sprinkler maintenance company and follow their instructions;
- Arrange a call out as soon as possible;
- Take steps to dry your room, which may include using a heater and dehumidifier;
- Take steps to understand what caused the accidental discharge;
- Ensure the sprinkler company notes the discharge in your log book.
- Take steps to prevent the incident from being repeated.
How can you protect your property from fire and water damage?
If you found the above article useful, then please feel free to check out our other guides. All of the guides listed under the Sprinkler Academy for Developers and Regulators are free.
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