DIY Doctor UK DIY Forums

I’ve spotted brown thick sludge in the header tank. No animals etc.

I fitted new radiators throughout the house about 4 months ago and put some inhibitor in the system. I didn’t flush the system before I added the inhibitor. I also didn’t balance the tags as they all seemed to get nice and hot. The radiators work fine.

I’ve ordered some x400. I plan to clean the header tank, then flush the system and add some x200.

Does this all seem ok?

There are two oxides of iron, ferrous and ferric one is yellow and one is black, mix the two and you have brown or red often called rust.

If you use water as the hydraulic fluid then it will cause a brown oxide to form, so we instead use a water inhibitor mix, this stops the oxides forming, however it needs topping up if you do any work on the system.

With a header tank easy, but with a sealed system not so easy, when I renewed a lock shield valve for a TRV I refilled the radiator with inhibitor before turning the valves back on. How it should be added not a clue.