Corrosion Prevention

Modern closed-circuit hydronic heating systems consist of many different materials and products sourced from numerous global suppliers. This is to reduce costs, increase life expectancy and improve system efficiency. In general, due diligence and a considered approach are placed into the specification of the products that are to be used in a system, but sometimes less thought is put into the system's water quality.

The majority of systems today will consist of a mixture of metal and plastic components, the type of inhibitors used in these systems should be carefully considered. It is important the entire system is protected from corrosion as all systems containing metal components are susceptible to deterioration without careful system design and selection of inhibitors.

A further consideration is that some traditional water treatment inhibitors that are still in use today (albeit mainly in the commercial market) are harmful to human health and not environmentally friendly.

There are many considerations to ensure a complex mixed material system is protected from corrosion. To make this easy for the system installer, companies like Fernox UK have created mixed metal system inhibitor products. These products provide complete corrosion protection to the systems and are often safe for the user and environment, with correct use and the required levels-maintained, corrosion-related system problems can be completely eliminated. We are fortunate in New Zealand that most of our product suppliers have also partnered with reputable treatment suppliers, this can give us confidence that the systems we install, and service will last long into the future.

One area where we may be lacking in New Zealand is analysis of the condition of the water quality of the system, often because of how we were taught or just for simplicity a system service will consist of a top-up of inhibitors, rather than a check of the water quality. It is not widely known that most mixed metal inhibitors are not actually consumed by the system, and in an ideal world would not need annual top-ups. When doing this we risk not finding a system problem before it becomes a bigger issue.

Most inhibitor suppliers will have simple and cost-effective testing procedures for analysing the inhibitor concentration in a system. From this analysis of the water quality the installer can see what percentage of system inhibitor is still present in the system, if the system is only just short of the required amount, the normal top up may be all that is needed, however, the system is very low on inhibitor some more investigation may be needed.

If inhibitor levels are found to be low the likely cause is frequent top up, this could be manual by the homeowner or previous tradesman, or via an automatic make up water system. After working out how the fresh water is entering the system, the expansion and pressure relief systems may need to be checked for correct set up and function, along with confirmation that the system is watertight before re-dosing. If the cause of the leak cannot be found or repaired, a more frequent system water analysis and dosing programme will be required to prevent premature system and component failure.

Correct water quality in systems will be crucial to improving the life and reliability of your central heating systems, if this is managed correctly you and your clients will enjoy the benefits of reliable and efficient heating systems for many years to come.

More system treatment reading 

  • VDI2035 Part 2, is the authoritative guideline in Europe for the prevention of damage in waterbased heating systems
  • Fernox Video: How does Fernox Protector F1 work?
  • British Standard BS7593: A Code of Practice for Treatment of Water in Domestic Hot Water Central Heating Systems
  • UK Government’s Domestic Heating Compliance Guide – Part L