Clean drinking water is something most of us take for granted – we simply turn a tap on as and when required and presume that the water which comes out will be safe and hygienic. This confidence overlooks the complexity associated with designing and maintaining water systems that are then able to reliably provide clean water for the lifetime of a building.

Much of the complexity arises from the fact that water can become the perfect habitat for dangerous bacteria if it is allowed to lie stagnant at temperatures between 20°C and 45°C. This risk means that it is essential that water systems are designed in such a way that the water is kept moving and out of the dangerous temperature zone.

Large problems in large buildings

Achieving this in a ‘standard’ house is relatively straight forward, as the water rarely sits stagnant and doesn’t have to be transported long distances from its source. But it’s a whole other matter when we consider the water circulating through the extensive networks of high-rise buildings or in large facilities with contamination sensitive occupants, such as hospitals and care homes.

A recent study by Purdue University highlighted the importance of maintaining hygienic plumbing systems in large buildings when it looked into the impact of COVID-19. It found that in many buildings which had been shut down and left for long periods of time due to lockdown, the water in the pipes had stagnated and required flushing in order to remove potentially contaminated water prior to the property reopening. As businesses return to work, a lot of their attention will be focused on preventing transmission of the COVID-19 virus and it’s important that the water system’s role in maintaining a healthy environment is not overlooked.

Water Safety Plans

As water systems within large buildings require so much care and attention, the World Health Organization (WHO) recommends that every large facility should implement a Water Safety Plan (WSP).

An effective WSP will ensure that all risk factors are identified and that controls and monitoring processes are put in place to minimise any risks. The design of the system is central to protecting the water’s hygienic integrity, and the WHO points out that every effort should be made to construct new systems to support the implementation of WSPs – especially for large buildings and those that have been renovated.

Water system design

Previously safe water systems can quickly be compromised during renovations, as ‘dead-legs’ or ‘blind-ends’ can be inadvertently incorporated into the layout. A dead-leg is a run of pipework that is not commonly in use and blind-ends are lengths of pipe which have been terminated. If either of these are present in a system, then pockets of water will stagnate as the water in these sections of pipe will be cut off from the normal flow within the system.

Installing pipes in a loop configuration avoids this, as water is flushed through the whole local pipe network every time any water outlet on the loop is opened. This prevents stagnation and removes the potential of a dead-leg within a local network, making it a highly effective method for reducing the possibility of bacterial growth.

The WHO’s advice also points to the fact that large buildings can suffer from poor flow rates, which is often due to the length, diameter and layout of the pipes. The type of pipe that’s installed can also affect the flow rate. Multi-Layer Composite (MLC) pipes are advisable in larger buildings as the smooth internal walls create less friction than traditional copper pipes and therefore maintain a higher water pressure.

An additional benefit of MLC pipes is that they can be supplied in long coils that can be cut to specific lengths and can easily be bent and formed around obstacles, creating a joint-free pipe system between the water source and the outlet. Reducing the number of connections not only helps to increase confidence in a system that’s enclosed within a wall or ceiling, but it also means that smaller pipes can be used. Using smaller sized pipes provides key advantages, as less water is stored in the system and hot water can be delivered more quickly to the outlet, which also saves on the amount of water wasted whilst the user waits for the hot water delivery.

Knowing how the water system within a building is designed is essential in order to be aware of how the water could potentially become unhygienic. While risk factors can be minimised through clever design, WSPs are still vital in large buildings to make sure that the water system is continuously monitored in order to safeguard the health of the building’s users. As the Purdue University study indicated, an effective WSP will come into its own in times when normal operations are suspended and confused, as it will be able to flag up the potential hazards that might not be immediately obvious.

Dave Lancaster is senior segment manager - commercial at Uponor