The LWF Blog

Fire Safety Engineering for Design – Sprinkler Installation Planning – Part 253

September 22, 2025 10:35 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 252, LWF looked at how to calculate the basis of hydraulic demand for a sprinkler system. In part 253, we begin to discuss the water supply for a fire suppression/sprinkler system.

One of the most essential parts of a water-based fire suppression system, or sprinkler system, is an adequate water supply. If water isn’t available in sufficient quantities and for the required duration, a fire can grow and become uncontrolled.

There are three key factors of importance in relation to a water supply for a sprinkler system – reliability, flow rate and capacity (duration).

When considering water supply, it is directly connected to the level of hazard the sprinkler system has been installed to mitigate. The greater the hazard, the higher the water flow rate and capacity that will be required and, of course, the more important it is that the water supply is reliable.

The designations for the different types of water supply are:

• Single supply
• Superior supply
• Duplicate supply

These water supply designations are in order of increasing reliability. Any designation is likely to be suitable for light and ordinary hazard risks, but high hazard risks usually require superior or duplicate supplies to be in place.

The water supply for most sprinkler systems is obtained from one of the following sources:

• Town main
• Auto-booster pumps drawing from the town main (if approved)
• Auto-suction pumps drawing from suitable sources
• Elevated private reservoirs
• Gravity tanks
• Pressure tanks

An example of a single water supply might be:

• Fed from a town main, in turn fed from a single source
• An automatic suction pump drawing from a suitable source (single)
• An automatic booster pump drawing from a town main fed from a single source (single)

Superior supplies include the following:

• Town main fed from more than one source and from both ends and not dependent on a common trunk main
• Two automatic suction pumps drawing from a suitable source
• Two automatic booster pumps drawing from a town main (fed from more than one source and from both ends and not dependent on a common trunk main)
• Elevated private reservoir
• Gravity tank
• Pressure tank (light and ordinary hazard risks only)

In part 254 of LWF’s series on fire engineering we will continue to discuss the water supplies for sprinkler systems, starting with duplicate supplies. 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.