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
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.
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