Why is the water black when I bleed my radiators?

Question

I’ve just gone round bleeding them and the water coming out was really dark and murky, which caught me off guard. The heating still works, but now I’m worried that colour means something’s wrong inside the system.

David · Answer

Hi

So black murky water within your heating system we call sludge. 
Sludge is 98% magnetic due to the properties being rust from the internals of your radiators boiler pipework etc, when you add air water and metal together obviously overtime it creates said rust. 
When your heating system is at the point where it is quite sludgy we would highly recommend a power flush. This will clear the system water using a strong cleaner and then inhibitor would be added at the end.
It does affect the use of the heating system, i.e. will take longer to circulate the heat and make the pump and other vowels within the system struggle however the heating system as you say will still work.
Many thanks, Oliver Plumbing and Heating

Aaron · Answer

It’s rust from the water inside the radiators. A little bit is okay but check the bottom of your radiators in the middle to see if they get hot when the heating is fully hot. If there are cold spots you may have a build up of sludge in the system

Keith · Answer

Because the system requires cleaning with chemicals

Nadeem · Answer

System needs cleaning.

1) filter has not been cleaned 
2) no inhibitor in system 
3) old radiators may cause more build up. 
4) system flush may resolve the issues

Dan · Answer

It’s the rust from inside the heating system, normally from inside radiators

Jason · Answer

The most likely cause is sludge deposits in your heating system which could require poweflushing and adding system filter (if one isn’t there )

Mehdi · Answer

Hi,

You system is full of sledge needs a  whole system power flush

Why is the water black when I bleed my radiators?

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