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Cat 4 Fire Sprinklers 

Base Fire Sprinklers design, supply, install and maintain Category 4 fire sprinkler systems.

Base Fire Sprinklers can help you to understand your obligations under the recently introduced Category 4 fire sprinkler regulations, which apply to tall residential buildings including blocks of flats over 18 metres high.


Category 4 sprinkler rules were added as part of British Standard BS 9251:2021 and most websites still only refer to the pre-existing Categories 1-3. We welcome all enquiries if you have any questions about the new category and how it applies to you.


We would recommend complying with the minimum requirements of Category 4 in any large development, conversion, refurbishment or extension.


Fire sprinkler legislation is likely to tighten further in the coming years, especially in England where the rules have been less strict than in Wales and Scotland.

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Call now on 0800 009 6906.

I would like to compliment the engineers that we have met on site who have completed the servicing and repair works on the systems....I cannot find one area where I would be unhappy with the service we have received.

Jack Newell, Weaver Vale Housing Trust


Construction site

Cat 1 Fire Sprinkler Systems


Why Was Category 4 Introduced?

Category 4 applies to tall buildings (height over 18m) and was created as a response to the Grenfell Tower tragedy. More generally, it aims to achieve several key outcomes:


  • Improve resilience and mitigate risks in high-rise buildings similar to Grenfell Tower

  • Align building standards with Fire and Rescue Service access and response time guidance

  • Ensure consistency with BS9251:2021 for the design, installation and maintenance of automatic residential sprinkler systems


The stricter rules of Category 4 mean sprinkler heads may also be needed in plant rooms and bike sheds (depending on the lining used in the construction of the room) and in communal areas such as corridors and stairways, which are typically considered 'sterile'.

Sprinkler Categories

What are the Category 4 sprinkler rules?


The major difference in the Category 4 sprinkler rules is the duration of water supply that must be stored in order to feed the system in the event of a fire; the other criteria are the same as the Category 3 rules:


  • Calculations based on 2-4 sprinkler heads operating simultaneously

  • Water flow rate of approx. 150-300 litres per minute

  • Storage tank size of  15.00- 25.00 cubic metres

  • Minimum duration of 60 minutes of stored water supply


In order to meet this increased duration, multiple water tanks will be needed. Because of this, Category 4 sprinkler system designs should always include a minimum of two water tanks of the specified size.


Enhanced water supply for Category 4 sprinklers


The greater capacity is part of the enhanced water supply used in Category 4 sprinkler installations, which improves reliability and failover redundancy in high-rise residential sprinkler systems.


Some of the characteristics of this enhanced water supply include:


  • Two or more tanks supplying half the system capacity each

  • Two or more pumps that can draw water from either tank

  • Ability to isolate one tank and/or one pump for maintenance


It's important to work with a fire sprinkler installer who understands the greater complexity of Category 4 sprinkler systems, in order to design the system so that each component can be isolated for servicing or repairs.


Base Fire Sprinklers have the engineering expertise to do this, backed up by sophisticated AutoCAD software so that we can design your Cat 4 sprinkler system in a virtual setting before we install the hardware on your premises.


Do I need Category 4 sprinklers?


If you are developing or refurbishing a residential building 18 metres or more in height, it's likely that you fall within the remit of Category 4.


We appreciate that this is still a relatively new category, and many developers might not be familiar with the eligibility criteria or the mandatory requirements.


Our expert engineers are here to help. If you want a second opinion on whether you should install Category 4 fire sprinklers, get in touch and we'll help you to decide if your property is eligible or not.

We are Accredited and Experienced

It is vital that your fire suppression system is designed and installed by an accredited sprinkler company to ensure you have complied with the frequently evolving regulations, insurance requirement and technical .

Contact Base Fire Sprinklers Today


If you have any questions at all regarding Category 4 fire sprinklers, please contact us today. All enquiries are welcome and we will be happy to help you determine whether your development falls under Category 1, 2, 3 or 4 under the updated legislation.


Base Fire Sprinklers offer a complete fire sprinkler design, supply, installation and maintenance service, helping you to navigate the changing rules, which are likely to tighten further in the future.


For all enquiries relating to any category of sprinkler system installation, and to benefit from the expertise of our engineers, get in touch today and Base Fire Sprinklers will be by your side.

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