The LWF Blog
Fire Safety Engineering for Design – Sprinkler Systems – Part 238
June 9, 2025 10:43 amLWF’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 237, LWF gave an overview of wet installations and alternate wet and dry installations. In part 238, we talk about dry installations, tail-end alternate and tail-end dry systems.
Dry sprinkler installations
A dry sprinkler installation is an option which should only be considered if wet or alternate wet and dry installations are not appropriate (and it should be noted that alternate wet and dry systems are inappropriate for installations in the UK, for high-hazard storage risks or where the temperature might exceed 70 °C.
The pipework of a dry sprinkler system is permanently charged with air, much like an alternate wet and dry system is during the winter months. A dry sprinkler system is suitable for installation where weather conditions mean it is likely to be subject to permanent frost conditions and may be used in cold stores, multi-storey car parks, etc.
Conversely, it is also suitable for areas where the temperature is likely to exceed 70 °C, such as drying ovens.
Tail-end alternate or tail-end dry systems
It may be the case that some installation environments are suitable in the main for a standard wet sprinkler installation, except for a small area. Where limited areas are likely to be subject to sub-zero conditions either on an occasional or permanent basis, then a small alternate or dry system may be suitable, as an extension to the wet system.
Such extensions are called tail-end alternate or tail-end dry systems, depending on their function. As with full alternate or dry systems, the provisions and restrictions noted for full systems will equally apply to the tail-end systems.
Pre-action installations
A pre-action sprinkler installation is a dry installation which also incorporates other measures designed to pre-arm the system in the event of fire detection by the fire alarm system. For this type of sprinkler to work, it should be installed in the same area as an electronic fire detection system. The integration between the two systems must comply with appropriate standards to ensure it will operate as intended when it is needed.
In part 239 of LWF’s series on fire engineering we will continue to discuss pre-action sprinkler installations. 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.