Sprinklers, their reliability and performance specifications

The requirement for reliable fire safety systems is clear.? These systems are typically provided to meet life safety aims, but also in many cases they are needed for insurance requirements or to protect historic buildings from fire for example.?Sprinklers, and arguably all active fire suppression systems, are a key part in achieving these goals.?Their reliability is determined through their design, how they are maintained and how they are managed in order to verify they are operational. ?

Sprinklers have been around for over 160 years[1].? They have a proven track record.? Buildings with sprinklers, simply put, have an order of magnitude improvement in safety (research[2], statistics[3]). In other words, buildings (generally) have a ten-fold better safety record (90% reduction in civilian fire death rates), with sprinklers than without.?It therefore begs the question - why don’t we include sprinklers in all buildings everywhere??If they were ‘cheap’ to install, didn’t take up too much room, and didn’t accidentally discharge or leak it would be self-evident they should be provided.?The question arises; what are the barriers preventing the more widespread use of sprinklers in the UK??

The sprinkler industry proactively introduced residential sprinkler design standards in 2005[4].?They provided a solution which effectively allows pipework to be plumbed off the domestic supply (variations are possible), which has been a game changer for the UK[5].?Given sprinklers are now so widely accepted and ubiquitous in new residential developments, their inclusion in all flats (not just above 11m) should be prioritised.?That will deliver real safety benefits in the somewhat overlooked, but still significant low-rise residential market.??So, if sprinklers have been a universal success for nearly 20 years in flats, why aren’t they used more often in schools, hospitals, hotels and smaller retail units in particular??

Approved Document B[6] provides guidance for the use of sprinklers – which in my view oversimplifies and places disproportionate benefit in two key parts of a system; water supplies and pumps.? It reinforces a tick box approach to fire safety, where a system is deemed ‘noncompliant’ and therefore through inference ‘unsafe’ if duplicate power, water supplies, tanks and pumps are not included.?What is this based on??Sprinkler standards have a long history (which I am not an expert on).? What is clear is that the innovative approach to residential sprinklers (i.e. within buildings accounting for 75% of fatalities[7]), has not been applied elsewhere in UK sprinkler standards - at least through my 25-year career.?Sprinklers at one time no doubt required large water tanks and pumps as water supplies themselves had low pressure, low flow and no doubt weren’t very ‘reliable’. Before the 19th century, the UK's water supply was primarily localised, with households relying on wells, local streams, and rainwater harvesting. ?A lot has changed in UK infrastructure over the last 35 years, since the introduction of the Water Act 1989[8].? Low pressure water distribution systems, and widespread power cuts are now very rare.?The UK now has, and is an improving trend, one of Europe’s most reliable water & power supplies[9].?

How reliable does a system need to be?? If water and power supplies were 100% reliable, would we still be needing additional tanks and pumps? National Grid have a 99.99995% transmission reliability – to the customer this can result in a loss of power for 15 minutes a year[10], or a probability of failure as 0.0000285.? This is extremely unlikely.? Are additional water tanks and generators therefore needed? There is no evidence I am aware of that adding these components to sprinkler systems will make them any safer.? Adding more items to maintain means more to go wrong – and more chance of the system being turned off either through a leak, a costly fault or ignorance as the system is too complex to look after.? PD 7974.7[11] reports that analyses of sprinkler system failures (which themselves are relatively rare) most sprinkler system failures are associated with sprinklers being turned off.?

How much water is needed??The NFCC[12] report that most fires are controlled by 1 head operating, and 95% by 5 or less heads.? BS EN 12845[13] recommends (for example) 5mm/min/m2 (Ordinary Hazard), which equates to 300l/min for 5 heads operating.? It’s logical to assume 95% of all fires are controlled by 300l/min.? Why therefore would the same standards ‘require’ 1350l/min as the minimum flow rate – what is it based on?? One could argue the standard itself is making it too difficult to deliver simple & cost-effective sprinklers; actually resulting in less sprinklers going in.? A less safe outcome.?

Should we simplify how we deliver sprinklers in the UK and tolerate system reliability using UK infrastructure?? In my assessments, mains fed water and power supply systems are adequate for life safety. ?A building with sprinklers is much safer than a building without.? There will always be a sound case for boosted sprinkler systems (therefore electric pumps), particularly for multi-storey developments, but a solution with generators, duplicate pumps and water tanks is somewhat outdated, unwarranted and an over specification - with little if any safety benefit.?

?"the best part is no part and the less parts the better".?Applying this mantra to sprinkler design, considering the evolution of UK water and power infrastructure, is now needed.??A completely ‘fail proof’ system doesn’t exist of course, but one which is reliable enough, is also good enough.?

1. https://canutesoft.com/information-and-resources/history-of-fire-sprinkler-systems-1881-1888
2. Open plan flat layouts Assessing life safety? in the event of fire, NHBC Foundation 2009 (Figure 11)
3. https://www.nfpa.org/education-and-research/research/nfpa-research/fire-statistical-reports/us-experience-with-sprinklers
4. BS 9251:2005: Sprinkler systems for residential and domestic occupancies — ?Code of practice
5. Efficiency and Effectiveness of Sprinkler Systems in the United Kingdom:? An Analysis from Fire Service Data, Incidence of Deaths and Injuries in Sprinklered Buildings: ?A Supplementary Report March 2019
6. HM Government, The Building Regulations 2010, Approved Document B: Fire safety Volume 2 – Buildings other than dwellings, 2019 edition incorporating 2020 and 2022 amendments (+2024 amendment booklet).
7. https://www.gov.uk/government/statistics/fire-and-rescue-incident-statistics-year-ending-september-2023/fire-and-rescue-incident-statistics-england-year-ending-september-2023#:~:text=Fire%2Drelated%20fatalities%20in%20dwelling,216%20in%20the%20previous%20year.
8. Water Act of 1989, https://www.legislation.gov.uk/ukpga/1989/15/contents
9. https://publications.parliament.uk/pa/ld201415/ldselect/ldsctech/121/12106.htm
10. https://annualreview2019.ukpowernetworks.co.uk/annualreview2019/operational-performance/network-reliability
11. PD 7974: Part 7, ‘Application of fire safety principles to the design of buildings. Probabilistic risk assessment’, 2019
12. Efficiency and Effectiveness of Sprinkler Systems in the United Kingdom:? An Analysis from Fire Service Data, Incidence of Deaths and Injuries in Sprinklered Buildings: ?May 2017
13. BS EN 12845:2015+A1:2019 Fixed firefighting systems. Automatic sprinkler systems. Design, installation and maintenance
14. https://everflowutilities.com/help-support/blogs/a-brief-history-of-water-supply-in-the-uk#:~:text=Before%20the%2019th%20century%2C%20the,these%20methods%20quickly%20became%20inadequate.