Can I Use Softened Water in my Boiler

Softened water in my boiler, will this cause a problem?   –  In short NO!   –  It will help.

Recent research supports that softened water (base-exchange) WILL NOT typically be detrimental to a boiler heat exchanger.

Indeed Veissmann boilers actually ask for the boiler to be filled with softened water during the installation, (they will even hire a water softener to the installer to enable them to use softened water).

For many years it has be thought that softened water increased corrosion within aluminium boiler heat exchangers. This myth is now being dismantled.

The British Standards Institute corrosion report dated 12th December 2012, shows that in the long term softened water has no adverse effect on aluminium heat exchangers.

This myth stems from an outdated British Standard BS7593:1992. This standard was revised in 2006 which now includes that softened water can be used providing a suitable chemical inhibitor is used. It appears that some boiler manufacturers still base some of there concerns around this confusion, and the 1992 version. The main corrosion inhibitors, such as Fernox and Sentinel, for years have not had a need to change or consider softened water in their formulations. Consequently it has been easier to say nothing.

But, now Fernox have released a technical bulletin (number 21) which includes the following extract:

“Fernox technical bulletin 21: When a central heating system is filled with base exchanged softened water, Fernox Protector F1 will adequately protect the heating system as long as it is correctly dosed and maintained throughout the life of the system. The correct dose rate of Fernox Protector F1 can be verified using either a Protector Test Kit or a Fernox System Health Check, both available from plumbing merchants.”

Sentinel has a similar statement:

“Sentinel X100, the benchmark of quality inhibitors treatments, was specially formulated to be able to control corrosion and inhibit scale formation in fill-water of any quality, including base-exchange softened water. Applying and maintaining the correct dose of X100 will protect your system, ensuring it remains quiet, reliable, effective and energy-efficient for its entire service life.”

Some boiler manufacturers are beginning to shift there stance, from “cannot” to it is “not advised”. This is actually a relaxation.

The following frequently asked question of Worcester Bosch has what appears to be an ambiguity:

“Should I fit a water softener to my boiler?

Water softeners are now commonly used, especially in hard water areas around the UK.

With a condensing boiler, if you intend to use a softener unit you must remember that due to the change in ph level, it would be unwise to fill your central heating system with such water. This will implicate the longevity of your central heating system and pipe work.

Therefore it is wise, when adding water using the filling loop to your condensing boiler, that this is fitted prior to the softener unit.

It is acceptable to pass softened water through the domestic heat exchanger side of the boiler with no negative affects“

Reference Worcester Bosch: Should I fit a water softener to my boiler?

So do we recommend a boiler for you to use with a water softener

No, we specialise in Water Treatment.

I have already mentioned Viessmann, but there are more who do not have entrenched issues with softened water, such as Grant UK, Ferroli and Vaillant.

We recommend that before you purchase your new, or replacement, boiler that you take advice from the manufacturer of the boiler, you may be considering to have installed.

BEWARE some plumbers and heating engineers may not to be up to speed with the current situation of using softened water in boilers. The latest information is now being communicated through trade publications such as “Professional Plumbing and Heating Installer” July 2013 and the H & V News article H and v p 34 2 oct 2013

For more information visit “The Ministry of Common Sense“ 

The UKWTA say:

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.

Energy Saving Trust

In the last few years, tremendous progress has been made to identify that softened water really has a place in water treatment for modern high efficiency heating systems and boilers. Progress is slow but proceeding, the Energy Saving Trust wish to endorse water softeners but require the Corrosion Inhibitor suppliers to provide a BuildCert  testing standard.  Work in Progress.

Studies show that using hard water waste energy. Hence increased carbon emissions.

The UKWTA states on their website that:

“Ion exchange water softeners effectively remove the hardness salts which lead to lime-scale formation, for example as encrustation around taps, in heating systems and kettles – and sometimes causing “kettling”, boiler noise, in central heating boilers.

The UKWTA has demonstrated how lime-scale build-up has a major impact on reducing the efficiency of domestic water heating appliances – so much so that the government changed the UK Building Regulations (the Domestic Heating Compliance Guide – published May 2006) to require treatment of the feed water to water heaters in hard water areas to inhibit lime-scale formation.”

Carbon Trust advises on energy efficiency

The Financial Mail on Sunday published on the 3rd March 2013 an article titled “Forget double-glazing or solar panels, you can make huge savings by blitzing limescale“.

Here the article says:

“Research by the University of Plymouth found that a boiler with no limescale took 90 minutes a day to supply the average home’s hot water, while a boiler with 5 mm of scale took more than four hours. With 10 mm of scale, this rose to more than six hours, adding hundreds of pounds to a household’s annual gas bill.

In 2006, the Government required new homes in hard water regions to have water softeners installed. Several local authorities are now putting them in during council property refits.”

Further information

Harveys Water Softeners – Corrosion report

Benefits of fitting a Water Softener – Not just beneficial to energy saving

Water Softening systems – The best Home Improvement

Other Useful links

Water softening systems – choices and prices

The best water softening systems

Customer reviews

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