Water treatment
Water quality essentials
Proper water treatment should form the basis of any commercial heating maintenance programme, ensuring the ongoing efficiency and lifespan of a water heater and its components. Here, Chris Meir, sales director at Andrews Water Heaters discusses some of the most common water quality issues and how to combat them
programme in place that effectively meets their site’s demands. Recognising this knowledge gap, the Industrial and Commercial Energy Association (ICOM) recently published its new Commercial Water Treatment Guide which aims to combat this issue in commercial heating systems. While this document refers specifically to commercial boilers, the guidance
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can also be applied to water heaters. However, there are many other solutions available for water heaters above and beyond what is discussed in the ICOM guide. For this reason, consultants and contractors should also refer to manufacturer guidelines and consult 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, silt and sludge.
Limescale
Almost 60% of the UK’s water supply can be graded as ‘hard water’ which contains high levels of minerals such as calcium and magnesium. These minerals 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%. To combat these effects, Andrews Water Heaters recommends treating system water when the 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
or businesses that consume a large amount of hot water, such as hotels and leisure centres, impaired operation of water heating equipment can have significant consequences. Nevertheless, many do not have a
and can harbour bacteria, making them harder to clean. This is particularly inconvenient for businesses with a number of bathrooms, such as hotels.
Inhibitors
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.
Conditioners
An alternative treatment is the use of a physical water conditioner, which exposes the system water to a low level magnetic or radio field upon entry. This field makes impurities in the water clump together. Limescale-causing minerals are more likely to stick to this surface and stay suspended in the water, rather than form a 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. 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.
Sludge
While limescale is the main factor to consider for a water heating system, silt and sludge can also collect inside a water storage tank and can cause similar problems regarding impaired system performance and added 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 magnetic 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. Having a reliable supply of hot water is crucial for any business. With that in mind, an effective water treatment programme should be top priority for commercial building managers, to combat the damaging effects of sludge and limescale.
Having an updated ICOM guide to refer to is a step forward for water There is a wide range of solutions available for water treatment in water heaters
treatment practices, but it is also the role of the consultant and contractor to educate customers on its importance and drive up standards of water quality.
32 August 2017
www.heatingandventilating.net
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