If proper maintenance and servicing is not carried out, modern central heating systems can have their life span reduced to less than 10 years.
A chemical reaction between the metals used within the central heating system and the water in the system can cause corrosion (rust).
Steel is corroded by the action of Oxygen and water (or moisture), which forms Iron Oxide (rust) and this can cause problems especially with radiators and heating systems. Rust can happen very soon after introducing water into the system; however this process can be significantly speeded up if there is also air in the system.
To check for corrosion, simply drain a large glass of water from the system and check the water colour. Clear straw or pale Grey is normal, black indicates the presence of some sludge or Magnetite, but a rusty colour indicates corrosion.
If you see corrosion or sludge then you need to add a corrosion inhibitor, it is best to firstly drain the system and rinse out any sludge and any corrosion deposits. There are cleaners that can be added which will cleanse the system after a couple of days use, drain down and fill up. Lastly add the inhibitor.
If your system is older than 6 Years, it may need to be power flushed or cleansed.
Adding the corrosion inhibitor is not difficult, turn off the heating system and isolate the water supply to the feed and expansion tank. Unvented systems may require a dosing vessel or a specific type of dosing system. Some use a skeleton gun to inject in to radiators or filling loops.
Drain off the water until the tank is empty, add the inhibitor to the tank and restore the water supply, turn on the heating system which will circulate the inhibitor through the system.
For older systems, it is a good idea to flush the system through by draining and refilling repeatedly until the water runs clear. Once it is clear, add the inhibitor.