The LWF Blog

Fire Safety Engineering for Design – Sprinkler Systems – Part 242

July 7, 2025 10:23 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 241, LWF talked about the various components that make up a sprinkler system. In part 242, we continue to look at pipework and components of sprinkler systems and their usability in different scenarios.

When progressing the installation of a sprinkler design, it is important that good practice is followed at all times. When welding pipework, in-situ welding should be avoided if at all possible, due to potential issues with quality control. In-situ welding is also a fire risk in its own right and should be carefully managed in any circumstances.

The welded prefabrication should be carefully monitored for quality and avoid common techniques such as set-in sockets and ‘cut and shut’ direction changes, as they can impair the flow of water through the pipework.

Pipe materials and jointing methods should be considered carefully and the best option available chosen, when considering the following factors:

• Material cost and availability
• Ease of installation
• Experience and hindsight
• Flexibility for site variances
• The avoidance of any future issues with maintenance

The appropriate consideration of all relevant factors means that a common approach tends to be followed within the industry in the UK.

A typical wet installation might include:

• Underground feed main in high-performance polyethylene pipework (HPPE) with fusion-welded joints and fittings
• Installation pipework installed downstream of the alarm valve in black medium-grade steel tube to BS EN 10255
• Mains larger than 50 mm diameter to have welded branches and sockets, using mechanical grooved joints for adjoining pipework and to plant items with flanges
• Pipework of less than 50 mm to be fabricated with screwed joints and joined with screwed fittings, as per BS EN 10226-1 and BS EN 10242 respectively

While flexible connectors to sprinkler heads have become increasingly popular and offers a number of benefits when installing a sprinkler system at the second fix stage of a project, there are also issues which can detrimentally affect the operation of a sprinkler system in a fire.

The flexible connection may be poorly-fitted and requiring adjustment. They should not be installed above large plasterboard areas without an appropriate number of access hatches for maintenance and visual inspection. Due to these potential issues, many insurers do not permit their use.

In part 243 of LWF’s series on fire engineering we will begin to look at installation planning for sprinkler protection. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.