Frequently Asked Questions

Water treatment – What do I need to do?


If you live in a hard water area, (defined as total hardness greater than 200mg/l), to comply with Part L of Schedule I of the Building Regulations, the feed water to water heaters and boilers needs to be treated to prevent limescale formation when the primary space heating or hot water appliance is next replaced. New houses in hard water areas should already have some provision for water treatment. Details can be found in the Domestic Heating Compliance Guide published May 2006.

To comply with British Standard BS 7593:2006 Code of practice for treatment of water in domestic hot water central heating systems a corrosion inhibitor should be added to all wet central heating systems at the time of final system fill. Additionally, new systems should first be flushed with a cleaner to remove installation debris and flux residues, and older systems should be flushed with a cleanser (preferably with powered assistance) to remove sludge prior boiler replacement.


How can I find out my water hardness?


Contact your local water utility, who may make a small charge for this service, or use a hardness measurement test kit such as those often provided by local water softener suppliers/distributors or included with domestic appliances (washing machines and/or dishwashers).


Which scale prevention products work best?


Performance depends upon water quality at the point of entry: Properly installed and maintained water softeners are particularly good at removing the calcium and magnesium salts which cause limescale. Phosphate dosing devices are effective but leave the water with slightly increased phosphate content. Although it is generally understood that water conditioners do not completely prevent lime-scale build-up, when installed correctly they can provide a very high level of satisfaction. Some water conditioners, and filter products in particular, are better at preventing silica and/or phosphate derived scale than other products. For advice on selection of the product best suited to your needs consult UKWTA member companies.


Is softened water safe to drink?


Fitting a separate hard water drinking tap is not required by regulation, except in exceptionally hard water areas (above 400mg/l) where the Sodium content of the treated water (increased due to the softening process) exceeds the level laid down in the Water Supply (Water Quality) Regulations 2000. Fitting a separate drinking water tap is currently recommended by the UK Dept of Health, WRAS and the UKWTA.


Will fitting a softener help my eczema?


Whilst there is anecdotal evidence that softening water may have a positive effect in reducing the symptoms of atopic eczema – it is not clear whether this may derive from the reduction in hardness salts in washing/bathing water, or less washing powder residue in clothing – the UKWTA does not wish to prejudice the outcome of on ongoing clinical field trial being sponsored by the Department of Health to investigate.


Is softened water more corrosive than untreated tap water?


Generally, No! Naturally soft waters of low alkalinity and those from an ion-exchange softener can have increased potential for corrosion. The pH of these waters has tendency to become more alkaline when heated in open vessel – water of pH more alkaline than 8.4 is corrosive towards aluminium. Softening water does not significantly increase pH. The Water Supply (Water Quality) Regulations 2000 allow mains water to be up to pH 10 in England and Wales (pH 9.5 in Scotland). Recent testing has shown that softening water may actually make it less corrosive towards typical heating system metals, such as iron and copper, as it removes heavy metal contaminants which can accelerate corrosion.


Is filtered water better for me than tap water?


Stringent regulations ensure that tap water in the UK is of a very high quality and is suitable for drinking. However, concerns about taste, odour, cloudiness and occasionally, adverse press publicity, are often cited as reasons why people to look to improve the quality to make it more appealing to drink. In simple terms, water is essential for health and maintaining a good hydration level is increasingly being recognised as important for mental and physical performance. Good hydration can help prevent headaches, constipation, kidney stones, heart disease and certain cancers. If filtering tap water makes you feel more positive about drinking it, which in turn leads you to consume water you otherwise might not drink, then it is considered beneficial.


Can I put softened water in my central heating system?


Yes! British Standard BS 7593:2006 Code of practice for treatment of water in domestic hot water central heating systems has recently been updated and now allows systems, including those with boilers with aluminium heat-exchangers, to be filled with softened water provided that a corrosion inhibitor specifically formulated for the purpose is added and properly maintained.


Why is my boiler manufacturer claiming that because I have a softener fitted my boiler warranty is invalidated?


Very few boiler manufacturers have carried out testing to access performance of their products with softened water. Historically, certain manufacturers of boilers with aluminium heat-exchangers have adopted the position that as British Standard BS 7593:1992 Code of practice for treatment of water in domestic hot water central heating systems prohibited the use of softened water in systems with aluminium, it is still unsafe to do so and claim any breach invalidates boiler warranty. (Interestingly, they make no comment on the suitability of boilers in areas of the country where the water is partially softened by the local water utility!). Other manufacturers, who use the same grades of aluminium in their products, have held the position for some time that there is no evidence of increased risk with artificially softened water. The UKWTA has written to all boiler manufacturers in an attempt to seek clarity. For consumers wishing to use water softeners, the UKWTA recommends only boilers with aluminium heat-exchangers from MTS-Ariston. Consumers should approach manufacturers direct for confirmation of suitability of boilers with stainless steel heat-exchangers.


Is it ok to use softened water in my dishwasher?


Yes! Where the appliance has a built-in softener, such as in a dishwasher, turn the setting to zero and do not add any additional salt. Click here for a confirmation letter from Worcester Bosch.


Is it ok to use softened water in appliances with aluminium components?


Yes! There is no evidence to indicate that softened water causes problems with aluminium. Click here to read the UKWTA position statement on softened water and aluminium.