The LWF Blog

Fire Safety Engineering for Design – Sprinkler Installation Planning – Part 250

September 1, 2025 10:48 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 249, LWF talked about the protection of atriums from fire using sprinklers. In part 250, we continue to discuss sprinkler protection by considering the three main styles of pipework for sprinkler systems.

There are three main types of pipework design for a sprinkler system installation. They are known as tree or terminal systems; gridded systems and looped systems.

Tree or terminal pipework systems are the most traditional way of feeding sprinkler systems. The sprinkler heads are fed singly or in groups from dead-end range pipes, which are fed from distribution pipes from the water supply.

They are hydraulically simple. The water to feed the operating sprinkler heads feeds through only those range and distribution pipes supplying them.

Gridded systems are those where the sprinklers are fed with water by tie pipes. The tie pipes are fed from more than one distribution main, which may be connected to the mains water supply, but may have other sources.

In terms of hydraulics, a gridded system is more complex than a tree system, due to the fact each sprinkler may be fed from more than one direction. This means that all the system’s pipework may be charged with water at the same time, even when the fire only requires operational sprinkler heads in the area of one tie pipe.

Looped systems may consist of one loop or multiple loops of pipework which consist of a pipe downstream of the sprinkler installation control valves which connects into a single or multiple loop pipe configuration. The range pipes feeding the sprinkler heads are fed by the loop pipes.

The appropriate diameter of pipework for looped or gridded systems should be ascertained by using full hydraulic calculations, as the rules for design of sprinkler systems do not provide a basis.

Loop, multiple-loop and grid-pipe configurations may not be used for dry and alternate wet and dry pipe sprinkler installations.

A gridded system can be an appropriate fiscal decision, as the hydraulic load may be spread over a greater number of pipes, each of which may be smaller in diameter than those in a tree system. A gridded system is best suited to particular types of building, such as large, high hazard risks with large bays and flat or only slightly-sloping roofs.

In part 251 of LWF’s series on fire engineering we will talk about pre-calculated pipe arrays and fully hydraulically calculated pipe arrays. 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.