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Heating Corrosion and Inhibitors

A few simple precautions can avoid heating corrosion which result in your system having problems like sludge build up and pinhole leaks.

Cause of corrosion

Air getting into the system actually speeds up deterioration as oxygen is one of the essential requirements for corrosion.You’ll know if air is getting in because the radiators will need bleeding to remove the air on a frequent basis.

Where the air gets in though is another matter. It can enter through a number of routes, but the most common are through the feed and expansion cistern in the loft, the vent pipe which hangs over it or a leaking joint beside the pump.

Unfortunately, whilst it is possible to identify these, it is usually a job for a professional heating engineer to put it right.

Testing for heating corrosion

It’s a good idea to add a corrosion inhibitor to reduce the gradual deterioration of the system. Test a sample of water from your system each year to see how corrosive it is. Place the sample in an old jam jar and put a shiny steel nail in it. Remember not to use a galvanised nail or the test won’t work. Put the lid back on and leave the jar for a week or so. If the water has turned orange and the nail is rusty, the water has too much oxygen and will be corroding the inside of your system in the same way. You’ll therefore need to put an additive into the system to reduce this.

Adding corrosion inhibitor

Adding heating corrosion inhibitorRead the manufacturer’s instructions carefully and add the appropriate amount of the corrosion inhibito liquid. With an open vent system, this is done by adding to the feed and expansion cistern.

For a sealed system, you can buy a cartridge of heating corrosion inhibitor which can be injected in via the air bleed valve on a radiator - again, you should carefully follow the manufacturer's instructions for this.

T&S Heating Limited