Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.


Water contains varying levels of calcium and magnesium depending on its source; the greater the levels, the “harder” the water. Water softeners turn hard water soft by removing virtually all the alkaline earth ions in exchange for sodium (“salt”) ions.

Many people install water softeners to filter out alkaline earth ions and so “soften” their water. Softening water has several practical benefits: lime scale in pipes and shower-heads is reduced; scum (found around the edge of the bath) is reduced; lather increases (with consequent savings on soap and shampoo) and some people simply prefer the “feel” of soft water. On the negative side: calcium and magnesium are major minerals vital for the maintenance of good health. The Water Supply (Water Fittings) Regulations 1999 stipulate that homes with water softeners should retain at least one “hard water” source for drinking.

Another type of product, magnetic or electromagnetic water conditioners, are claimed to work in a different way. They are attached around water pipes and are believed to encourage alkaline earth ions to clump together, instead of sticking to the sides of the pipes. The ASA and CAP understand that magnetic or electromagnetic conditioning devices are not capable of “softening” water and as such should not be claimed to be equivalent to water softeners (International Bathrooms WTS b.v., November 2010).

In 2007, the ASA upheld complaints about an ad that claimed to inhibit the formation of limescale (J.E.M. Marketing, 10 January 2007). The ad claimed the water conditioner could “immediately prevent the build-up of lime scale” and “prevent the formation of new and additional scales in your pipes and appliances”. After taking expert advice, the ASA considered that the device was unable to prevent the build-up of limescale in a single-pass domestic system or to keep calcium in suspension as claimed in the ad.

That decision resulted in a stricter approach. The ASA understands that no universally accepted theory about how these devices operate and no evidence to support the contention that the devices can inhibit scale formation generally exists. The ASA has noted that, where the devices had been shown to work, the efficacy of the product often depended on circumstances beyond the advertiser’s control, for example the type of system used or the type of water flow.

Over the years, the ASA has repeatedly upheld complaints about ads claiming to “dissolve” or “eliminate“ limescale (Fast Systems Ltd, January 2005, and Arnhem Technologies, 28 November 2001). The ASA considered those claims too categorical and advised advertisers to avoid implying that water conditioners would completely eliminate limescale.

Marketers should also be wary of making claims that softened water is beneficial for specific skin conditions or health in general. One advertiser claimed that “Softened water can also greatly improve conditions such as dry skin, eczema and psoriasis” but was found to be unable to support such claims (Harvey Water Softeners Ltd, August 2011).

Marketers wanting to make efficacy claims for water conditioners may submit evidence to the Copy Advice team. The claims allowed will depend on the standard of the evidence and will normally have to include a disclaimer along the lines of “Results will vary, depending on the water system, water flow and water type in each household”.

Marketers who do not hold convincing trials should not state or imply efficacy for the products, through claims, visuals or product names. If the product name represents a claim of efficacy, for example “Scale Remover”, marketers should include a clear disclaimer, for example “Scale Remover has not been proven to remove existing limescale” (See Claims in product names). Claims that are likely to be interpreted as factual and appear in a testimonial must not mislead or be likely to mislead the consumer (Rule 3.47).

Although no set rules for testing procedures exist, trials should be representative of the range of environments in which the product will be marketed for use (for example residential single-pass systems). Marketers who are looking to conduct trials are strongly advised to submit their proposed research methodology to the CAP Copy Advice team before proceeding.


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