Background
Summary of Council decision:
Three issues were investigated, all of which were upheld.
Ad description
A brochure for Wash Water, a manufacturer of water conditioning and purifying systems, seen in September 2025. The brochure contained information about the Wash Water scale prevention products CleanScale XP and XP Pro. Text next to the heading “Features & Benefits” included the statements, “Targets and removes existing scale”, “Reduces hot water bills by 12-24% by removing existing scale” and “Can help improve certain skin conditions by reducing scale build up in your skins [sic] pores”.
Issue
Aquabion UK Ltd, a manufacturer of water conditioning systems, challenged whether the following claims were misleading and could be substantiated:
- “Targets and removes existing scale”;
- “Reduces hot water bills by 12-24% by removing existing scale”; and
- “Can help improve certain skin conditions by reducing scale build up in your skins [sic] pores”.
Response
1. WashUK Ltd t/a Wash Water stated that calcium dissolved into water when water was undersaturated with calcium ions. Water maintained an equilibrium either by causing scale or corrosion; that process was particularly noticeable when water was heated or experienced a change in pressure. Calcium ions present in water would either dissolve or be deposited as a solid (scale) depending on the environmental conditions.
Wash Water stated the CleanScale XP contained a helical metal catalytic core which worked by encouraging calcium to bind to carbonate and form insoluble crystals. As a result, there were fewer dissolved calcium ions remaining in the treated water, which would start to absorb and remove existing scale deposits in order to maintain equilibrium. They provided a confidential report which assessed a method of non-chemical water treatment that used the same helical core component as the CleanScale XP, a literature review, and a video from a supplier of water conditioning systems based in the US, to support their claim.
2. Wash Water stated many sources showed that calcium buildup caused energy waste in heating systems. From the evidence already provided, they believed that they had demonstrated that their product removed existing scale in hot water systems. They said that removing scale would improve energy consumption, and reduce costs. The percentage increase was dependent on the appliance and the amount of scale deposit present.
They provided a 2014 article which referenced research showing that 0.06 inches (1.5 mm) of limescale could decrease boiler efficiency by 11%. In relation to gas hot-water heaters, the article cited a 2010 study by the Battelle Memorial Institute (the Battelle study) which stated that over the course of 10 years, every 86 mg/l of calcium carbonate deposits led to a drop in efficiency of 4%, and a corresponding 4% rise in running costs. In very hard water areas with a higher calcium concentration, that could equate to a 24% drop in efficiency. They also provided two research studies in support of their claim. The first noted that scale in a specific region could increase energy usage by 4 to 12%. The second was the Battelle study referenced above, which they stated was the world’s most comprehensive study of the effects of a hard-water supply and was widely accepted by the water treatment industry. They also provided a summary of the Battelle study by the Water Quality Research Foundation.
3. Wash Water stated that an error had been made and the claim “can help improve certain skin conditions by reducing scale build up in your skins [sic] pores” should have read “can help improve certain skin conditions by reducing chlorine buildup in your skins [sic] pores”. To support the claim that was seen in the ad that referenced “reducing scale build up in your skins pores”, Wash Water provided three scientific studies which they believed demonstrated that surfactant deposits could increase irritation, and which investigated the behaviour of calcium carbonate particles in water.
To support the claim regarding chlorine, they provided two abstracts from research papers and one full scientific study. They also stated that their products were certified by the National Sanitation Foundation (NSF), an international organisation that provided testing, inspection, certification and advisory services to various industries. They said the carbon used in their product was certified to standard NSF/American National Standards Institute (ANSI) 42, which covered water filters that reduced aesthetic impurities such as chlorine and taste or odour.
Assessment
1. Upheld
The ASA considered that consumers would understand the claim “Targets and removes existing scale” to mean that the advertised product would actively target and remove pre-existing limescale deposits. We therefore expected them to hold robust evidence demonstrating that this was the case, such as relevant peer-reviewed research studies or systematic reviews.
We reviewed the evidence provided by Wash Water. We first assessed the report they provided, which detailed the results of installing a non-chemical water treatment (NCWT) device, which used the same core component as Wash Water’s product. The report concluded that the NCWT device reduced calcite build-up. However, the report did not contain information about the research methods used, or how calcite build-up was measured beyond a visual inspection. In order to substantiate the claim, we expected any evidence to use an objective method of measuring limescale build-up. In the absence of such data, we considered that a visual inspection alone was not sufficient evidence that the device actively prevented and removed limescale. The report focused on calcite build-up in a newly installed water heating element and did not consider whether an NCWT device could remove existing limescale. The report was not peer reviewed. For those reasons, we considered that it was not sufficient to substantiate the claim that Wash Water’s product could treat and remove existing limescale.
We next assessed the literature review, which summarised a range of papers that commented on the formation and cleaning of limescale in heat exchangers at industrial power plants. The review provided information about the chemical processes involved in the formation of limescale, and stated that in the presence of certain ions, calcium carbonate formed crystals which were unable to deposit themselves as scale. Whilst the review provided background information into the processes that resulted in scale formation, it did not specifically comment on the use and efficacy of water treatment devices such as those advertised by Wash Water. We therefore considered it was insufficient to substantiate the advertiser’s claim.
We then assessed the video Wash Water provided. The video showed a “field-test” by a US-based supplier of water conditioning systems, whose product used the same core component as Wash Water’s. The video showed a heat exchanger for a tankless heater system, which had had a water conditioner installed, being cut in half. The tankless heater had very little scale build-up after 36 months of use. The evidence was anecdotal, and as it involved a visual inspection of only one heater system, we considered it insufficient to substantiate the claim that the advertiser’s product could target and remove existing limescale.
Because we considered that the evidence provided was inadequate, we concluded that the claim that Wash Water’s water conditioning systems could target and remove existing limescale had not been substantiated and was misleading.
On that point, the ad breached CAP Code (Edition 12) rules 3.1 (Misleading advertising) and 3.7 (Substantiation).
2. Upheld
The ad stated, “Reduces hot water bills by 12-24% by removing existing scale”. We considered consumers would understand the claim to mean that by installing one of Wash Water’s devices in their home, they could make significant savings and reduce their hot water bill by at least 12 and up to 24%. In the absence of any specific time frame stated in the ad, we considered consumers would understand that the stated savings would apply to their current hot water bill. We therefore expected the advertiser to hold robust evidence to demonstrate that was the case. Such evidence should be specific to Wash Water’s product.
We reviewed the evidence provided. The first piece of evidence was an article written in 2014 which was intended to accompany a Continuous Professional Development (CPD) assessment. The article provided an overview of the topic of limescale prevention. It cited a 2011 report that found that a 1.5 mm coating of limescale on the heat exchanger of a boiler could reduce its efficiency by an average of 11%. However, because we had not seen the original report from which this claim originated, we could not assess its relevance. The article also summarised the key findings of the Battelle study, which Wash Water had provided in full and which we assessed separately. Because it was not a systematic review or piece of primary research itself, we considered that the 2014 article was not sufficient to substantiate the advertiser’s claim.
We next assessed the first scientific study provided by Wash Water. The study, conducted in 2017, examined how water hardness affects power consumption of water heater elements. The results demonstrated that limescale formation increased power consumption by approximately 4 to 12%, although the copy of the study we were provided was missing some tables of data. The study also investigated whether electronic descaler technology could inhibit the formation of limescale, and found minimal scale formation on heating elements when a descaling technology was used. However, we understood that the electronic descaling technology used in the study differed from the technology used in Wash Water’s product, and therefore the results of the descaling technology in the study could not be applied to the claims made in the ad. We therefore considered the study was insufficient to support the advertiser’s claim.
Finally, we assessed the Batelle study, which examined efficiency improvements in household water heaters from the use of softened water, and the subsequent effect on household fixtures and appliances. The study tested 10 gas water heaters, 10 electric water heaters, and 10 tankless gas water heaters. Half of each type of heater were tested on unsoftened water, and the remainder were tested using softened water. The study found that gas storage and tankless gas water heaters fed with unsoftened water had a noticeable decrease in efficiency. Data from the study was used to produce equations that predicted the efficiency of gas storage water heaters as a function of water hardness and daily household hot water use. The study estimated that gas storage water heaters using softened water could make energy cost savings of up to 24.2% over a 15-year life span, depending on the hardness of the water.
However, we understood that water conditioners, such as Wash Water’s product, did not produce softened water. We understood that water softeners generally functioned by removing calcium and magnesium ions from water and exchanging them for sodium ions. Water conditioners were claimed to encourage mineral ions in water to clump together rather than forming limescale. CAP’s guidance on water treatment devices stated that although it was theorised that the calcium and magnesium ions remained in the water in a different form, the ASA understood that no universally accepted theory about how such devices operated existed. As addressed in issue 1 above, we had not seen sufficient evidence to support claims that Wash Water’s device could prevent or remove limescale build-up, or behave in the same way as softened water. Because the estimated cost savings identified by the Battelle study were based on the use of softened water, we considered that they were not directly relevant to the advertised product. Furthermore, we understood the energy and cost savings estimated in the study applied to new gas storage water heaters with minimal scale build-up across a 15-year life span, rather than pre-existing, descaled systems. We therefore considered the Battelle study was insufficient to substantiate the claim “reduces hot water bills by 12-24% by removing existing scale”.
Because the evidence provided was not relevant to Wash Water’s product, we concluded that the claim “reduces hot water bills by 12-24% by removing existing scale” had not been substantiated and was misleading.
On that point, the ad breached CAP Code (Edition 12) rules 3.1 (Misleading advertising), 3.7 (Substantiation) and 3.11 (Exaggeration).
3. Upheld
We considered that consumers would understand the claim “can help improve certain skin conditions by reducing scale build up in your skins [sic] pores” to mean that installing a water treatment device could help improve some skin conditions by reducing the amount of limescale in water that would build up on the skin. We acknowledged that Wash Water stated there had been an error, and the claim should have referred to “reducing chlorine build up”. However, we assessed the ad as it would have been seen by consumers. We therefore expected to see evidence, in the form of methodologically robust studies, which were directly relevant to the benefits claimed in the ad.
We reviewed the three studies provided by Wash Water in support of the original claim “reducing scale build up in your skins [sic] pores”. The first study tested how surfactants, chemical compounds that reduce surface tension between liquids, stick to limestone. The second investigated whether precipitated calcium carbonate particles could help to pull dissolved calcium out of hard water. The copy we received of the third study, which measured how calcium isotopes swapped between water and common calcium carbonate minerals, was partial. Regardless, none of the studies provided referenced the effects of limescale on skin conditions or skin irritation. We therefore considered they were insufficient to substantiate the claim.
We acknowledged that Wash Water had provided evidence to substantiate the claim that referred to “reducing chlorine build up”. However, because that claim had not appeared in the ad, we considered that evidence was not relevant to how the ad would have been understood by consumers.
Because we considered that the evidence provided was inadequate, we concluded that the claim “can help improve certain skin conditions by reducing scale build up in your skins [sic] pores” had not been substantiated and was misleading.
On that point, the ad breached CAP Code (Edition 12) rules 3.1 (Misleading advertising) and 3.7 (Substantiation).
Action
The ad must not appear again in the form complained of. We told WashUK Ltd t/a Wash Water not to make claims that their water treatment systems could target and remove existing limescale, reduce hot water bills or help improve certain skin conditions in the absence of adequate substantiation.
