Harvey Water Softeners announces the results of a recent BSI Report and explains the implications for the use of softened water in central heating systems.

Harvey Water Softeners announces the results of a recent BSI Report and explains the implications for the use of softened water in central heating systems.


Since the 1980s, there has been disagreement within the professional water heating sector about the use of softened water in central heating systems with aluminium heat exchangers. The water softener manufacturers say that you can use softened water, while some of the chemical inhibitor manufacturers say you cannot.


In March, Harvey Water Softeners joined with members of the United Kingdom Water Treatment Association (UKWTA) and commissioned British Standards Institute (BSI) to carry out a test and prove that softened water is not corrosive to central heating systems with aluminium heat exchangers.


The results were announced by Harvey Bowden, chairman of Harvey Water Softeners (pictured), at the HHIC Annual Conference during the parliamentary reception at the House of Commons.


The report states: “Over the lifetime of a modern central heating system, filling with base-exchange softened hard mains water would appear to present no significantly greater risk of corrosion of system metals than filling with hard mains water.”


Harvey Water Softeners suggest the confusion dates back to the introduction of condensing boilers with their new-to-the-industry aluminium heat exchangers in the 1980’s, which suffered from a lot of corrosion problems.


In 1992, BSI published a British Standard BS 7593 in which it stated that softened water could not be used in systems with an aluminium heat exchanger, and boiler manufacturers adopted the policy of not permitting softened water in their boilers.


However, Harvey Water Softeners found that no representative from the water softening industry was on the committee writing the standard and subsequently, when the Chairman was asked why the clause had been included, he stated that it was requested by the chemical inhibitor manufacturers and it seemed like a good idea at the time. No evidence or technical support was given.


In 1993, a report by Philip Munn, now the proprietor of Midland Corrosion Services, showed that one of the causes of corrosion of aluminium heat exchangers was caused by chelating agents in the inhibitor. This is because the inhibitor is designed to work in hard water that contains calcium. The chelating agent combines with the calcium and prevents it forming scale. When used in softened water there is no calcium for the chelating agent to attach to, so it looks for the next nearest metal that it can dissolve, which of course is aluminium. So this showed that the chemical inhibitor itself was the cause of the corrosion problem.


The British Standard BS 7593 was corrected in 2006, but many boiler manufacturers have not changed their policy and continue to discourage the use of softened water.


Using softened water reduces the need for harsh cleaners and detergents that are used around the home making it an eco-friendly choice.


For central heating systems, the reduction in scale in the boiler, pipework, radiators and hot water cylinder prolongs the life of the heating system and makes it run more efficiently using less energy, says the company. With an average payback period of 5 years, water softeners have one of the quickest payback periods in the industry.


For more information visit the company's website


The video of the presentation given at the HHIC Annual Conference is available on youtube.