central heating

3 Feb 2007
Reaction score
United Kingdom
vented central heating system. pipes banging when hot water switched on and water and steam coming from expansion pipe into header tank also some rads upstairs need regular bleeding. i suspect this is gas/corrosion in system. any ideas please
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You're probably right. Sounds like a blockage where the feed pipe joins the circuit.
You can add desludging chems, run for a week and see what happens, but hard blockages can need the pipe cutting out.
thanks chris. someone suggested fernox i am going to give that a try. am i best to drain system and add to header tank or feed into bleed screw on rad. thanks
When heating is cold and you bleed upstairs rads do you get air then water, or air then nothing? If the latter then it will confirm blockage in cold fill.

I would recommend cutting it out and replacing ;)
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seems to be air and then nothing. if this is the case should i try fernox ,if not how do i locate the blockage thanks
actually come to think of it .i have had air then black sludge and also air and then nothing if that makes sense
Sounds to me it is a blockage in the cold fill. 99/100 times it is where the cold fill t's into the heating pipe work. it shouldn't be too big a job. maybe a little draining of the system and cut the T out and replace pipe work.

Once this is done put cleanser in the system and let flush through completley, drain fully then fill up with new inhibitor added ;)
possibly low head to .. raise the tank onto a stand .. this will help with the air build up .. ...

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