Boiler servicing

Water treatment explained: How to keep your heating system healthy

Buying a new boiler is a big investment, and not to be taken lightly, whether it’s a distress purchase because your old boiler has broken down and can’t be repaired, you have extended your home and need a bigger boiler to cope with more radiators or you are concerned about your carbon footprint and want to be more energy efficient.

What most people don’t consider, however, is the state of the system that the boiler is installed into. Existing pipework and radiators could be full of sludge, corrosion debris, bacterial growth and limescale – all of which can find its way into your brand new boiler. This can reduce energy efficiency and the worst case scenario is that all this debris ends up inside the heat exchanger and pipework in your new boiler, blocking it up and causing a breakdown.

Even when boilers are installed on a brand new central heating system, the heating engineer should clean the system thoroughly to remove installation debris, metal swarf (chips or filings), flux residue and grease, before the boiler is installed.

To ensure your system water remains in tip-top condition, there are a number of different water treatment methods that you can discuss with your installer.

  • Powerflushing – a powerflush is a cleaning process that removes sludge, rust and debris from the pipes and radiators in your heating system. If left, the sludge can cause corrosion and blockages, which can lead to boiler breakdowns. If the system is clean, the boiler will work more efficiently and radiators will heat up more effectively. Your installer should carry out a powerflush on your heating system before they fit a new boiler, otherwise all the debris that is dislodged could block the narrow tubes inside.
  • Inhibitor – once the heating system has been cleaned, it should be treated with an inhibitor to protect it and prevent further corrosion. If your central heating system is drained down, for example when removing a radiator to decorate a room, the inhibitor should be replaced.
  • System filter – a system filter should be fitted in your heating system as part of a Best Practice installation. It will collect magnetic and non-magnetic debris in the system water, before it enters the boiler. 
  • Limescale prevention – in hard water areas, Part L of the Building Regulations recommends that the cold water mains supply is treated with a scale prevention device, especially for combi boilers with take in water direct from the mains and heat it. This will ensure the limescale does not build up and block the heat exchanger in the boiler.

Benchmark checklist

When your installer has finished installing your boiler, they need to complete the Benchmark checklist to comply with the terms of the boiler’s warranty. This includes making a note of the water treatment they have carried out.

When you have your boiler serviced, your installer should also check to make sure the water in the heating system has still got the right amount of inhibitor and clean the system filter.

Benefits of a clean central heating system:
  • More efficient heating system
  • Boiler life extended
  • Lower gas bills
  • Boiler warranty compliance (check boiler warranty terms and condition and conditions)

You can read more about how to protect your boiler and heating system in the Heating and Hotwater Industry Council’s (HHIC) Consumer Guide.

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