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THE VIP TREATMENT Hard water – the hard facts

With over half of the UK’s main supply classed as hard water, eecve treatment plays an important role in the maintenance regime of any water heang system. Dan Marndale, Sales Director at Andrews Water Heaters, discusses some of the most common water quality issues and how to combat them.

or commercial buildings, such as leisure centres and hotels, a consistent hot water supply can be a business-critical service. However, despite this there are still a large number of commercial business owners who do not have a programme in place that effectively meets their site’s demands. In recognition of this knowledge gap, the Industrial and Commercial Energy Association (ICOM) published its new Commercial Water Treatment Guide earlier this year that aims to combat this issue in commercial heating systems. Whilst this document focuses on commercial boilers, ICOM are currently in the process of updating it to include water heating. With this being said it is also imperative for consultants and contractors to refer to manufacturer guidelines, along with consulting a water treatment specialist for specific advice on the most appropriate solution for their requirements. But as a starting point, several options are available for dealing with common issues such as limescale and sediment.

F Limescale

With approximately 60 per cent of the UK’s water supply graded as ‘hard water’, the majority of commercial buildings are vulnerable to performance-limiting limescale deposits.1 Hard water contains high levels of minerals such as calcium and magnesium. These can cause limescale deposits which coat the heat exchanger and other system components, resulting in blockages and potential equipment failure. Water heaters, of all types, are particularly susceptible to limescale formation, as it develops rapidly at higher temperatures. If system water is untreated, deposits can start to form as soon as the equipment begins being used. Not only does limescale damage components, but it also creates a layer of insulation, impairing the efficiency of the heater. In fact, according to British Standards (BS) 8558, tests have shown that limescale can reduce efficiency by up to 30 per cent.2

To combat these effects, Andrews Water Heaters recommends treating system water when its hardness reaches 150 parts per million, or 7-10 by the Clark Degrees scale. Aside from pushing up maintenance and energy costs, limescale is also unsightly when it builds up on shower heads, taps and basins and can harbour bacteria, making them harder to clean, resulting in malfunctioning mixer and taps. This is particularly inconvenient for businesses with a number of bathrooms, such as hotels, and jeopardises health and safety standards in hygiene-sensitive applications such as hospitals and food manufacturing.

Inhibitors base exchange

uPeriodic fiushing of the system will remove buildups but it is beer to prevent limescale and sediment in the flrst place.

Electrolytic scale inhibitors are an instant method for softening system water. The device is attached at the point of supply to the water heater and utilises the ion exchange process where the calcium in the water is replaced with sodium which is more soluble.

Despite being an effective way of treating limescale, raised sodium levels in drinking water is less than ideal, particularly for those with existing health problems such as elevated blood pressure. Therefore, it is imperative to fit a separate, dedicated drinking water supply in care homes or hospitals.


An alternative treatment is the use of a physical water conditioner, which exposes the system water to a low level magnetic field upon entry. This field makes impurities in the water collect together in smaller deposits. Limescale-causing minerals are more likely to stick to this surface and stay suspended in the water, rather than form limescale deposit on a heater’s components.

Unlike an inhibitor, this does not soften or change the chemical composition of the water itself. However, a white sludge known as ‘soft scale’ can accumulate when water is left to stand, for example in a water tank, but this is far easier to remove than limescale.

Both solutions have their pros and cons, but it is important to check that the device specified is compatible with the type of water heater installed, the required operating temperature and degree of hardness of the local water supply. It is also crucial to consider maintenance access; the longevity of the treatment and the impact turbulent water flow may have on the performance of the device.


While limescale is the main factor to consider for a water heating system, scale and sediment can also collect inside a water storage tank and can cause similar problems regarding impaired system performance and maintenance costs. Periodic flushing of the system will remove build-ups but it is better practice to prevent it circulating in the first place, for example by fitting a sediment filter at the point of entry. Water testing should form part of the ongoing maintenance programme. This ensures any water quality issues are detected early on, before they cause any costly damage to the system. It will also indicate if treatment has become less effective or stopped working altogether, helping to save money in the long run.

As the industry takes a step forward to improve water treatment practices with the ICOM guide, it is still vital for consultants and contractors to educate customers on this matter. An effective water treatment programme should always be top priority for any commercial building mangers; not only does it help ensure a supply of hot water to occupants, it also makes financial sense in the long run. Sources:

1. 2. 130-bs-8558-2011-water-use-in-domestic-buildings


uWater tesng should be done as a regular part of your maintenance schedule.

Water heaters, of all types, are parcularly suscepble to limescale formaon, as it develops rapidly at higher temperatures. If system water is untreated, deposits can start to form as soon as the equipment begins being used.

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