Press | Published on 2nd May 2017

Clean, protect, maintain, repeat.

The UK Government and the EU place great emphasis on the benefits of increased efficiencies, and reduced energy consumption, often through replacing or upgrading old inefficient appliances and systems. Whilst quite right, somewhat less “attractive” and headline-grabbing is maintaining and protecting these appliance and system efficiencies, despite the fact that they can deteriorate over time, particularly if adequate water treatment and protection are not undertaken at the time of installation, and increasingly, maintenance.

In extreme cases, this could mean that expected savings do not materialise, or drop off over time. It is well known that a boiler will have to work harder to supply the designed heat output to the property where radiators and pipework contain system debris, e.g. magnetite sludge. This situation can also lead to greater boiler cycling, increasing strain and wear on components (e.g. ignition), and resulting in greater heat losses through pre and post cycle fan purges.

So, protecting the appliance and system waterways is incredibly important if they are to operate at peak efficiency and performance throughout their lifetime. Research suggests that 80 per cent of all central heating system trouble is related directly or indirectly to sludge/debris in the system.

With that figure in mind, the Heating and Hot Water Industry Council (HHIC) together with our Water Treatment member group have issued a brief guide and a list of FAQ’s on the different types of WT chemicals and devices, with a view to educating the industry on the benefits of central heating care.

The guide covers three main areas – Cleaning, Protection and Maintenance.


A newly-installed central heating system may contain residual debris such as metal particles, solder residue etc. while an older system which has not been correctly protected with inhibitors may contain corrosion deposits in the form of  accumulated “sludge” in pipes, radiators etc.

BS 7593 specifies a number of cleaning methods, but in outline these are as follows –

  1. A conventional clean and flush

With all cleaning methods it is important to ensure that the cleaning agent and suspended debris are completely removed from the heating system as they may nullify the effect of any inhibitor subsequently used. Additionally, if the cleaner and suspended debris remain present in the system, the resultant mixture can lead to premature failure of system components (e.g. pumps). Loss of inhibitor effectiveness can also lead to gases being formed within the central heating circuit if corrosion re-occurs.


Once the system has been cleaned, it is important to ensure that the corrosion does not re-occur. The system water content should therefore be treated with a BuildCert  approved inhibitor to minimise corrosion. It is important to ensure that the inhibitor used is compatible with the boiler and other materials present in the heating system – as specified in the product instructions.

Lack of water treatment, particularly in hard water areas, can also lead to formation of limescale in the boiler’s heat exchanger, which can lead to reduced efficiency and boiler noise. Where the mains total water hardness exceeds 200 parts per million, provision should be made to treat the feed water to water heaters and the hot water circuit of combination boilers to reduce the rate of accumulation of limescale.


Once a system is cleaned and protected the concentration of inhibitor must be checked and maintained. Inhibitors are designed to have an extended lifetime in the heating system; however most water treatment manufacturers recommend checking concentration at annual boiler service intervals and will offer a simple test kit to do this.

It is also recommended that whenever WT products are used, a label is attached to the system to act as a record. The Benchmark Commissioning Checklist should also be used to record the inhibitor type and concentration used.

System filtration devices

A number of different filtration devices are now on the market, in addition to the chemical water treatments described above. These can incorporate magnetic or “cyclone” arrangements to remove fine particles suspended in the water circulating around the system. These devices help to maintain system cleanliness and provide an additional level of protection.

Water softeners and central heating boilers

Where a water softener is present in the dwelling, ensure that the heating system primary circuit is filled with mains water via the general bypass valve as required in BS 14743.

Refer to the boiler manufacturer’s instructions for any additional advice on softened water.

The full guide can be found at

The recent “Heat in Buildings” consultation identified water-treatment as a potential mandatory measure, to be phased in at a later stage of Regulation. Of course, we know that Part L, through the Domestic Building Services Compliance Guide, can be seen to mandate water-treatment already, but many HHIC member’s feel a greater legislative emphasis here is a step in the right direction. Increasingly, the need to enforce and solidify existing standards and codes of practice, rather than replace with new ones, is a hot topic of conversation within industry.