I have a closed pressurised central heating system that seems to be dificult to bleed all of the air out of. I have had lots of work done on the house which has necessitated lots of messing with the radiattors etc. This means that the system has been drained, filled or topped up regularly. The net effect is that I never seem to be able to get all of the air out of the system, hence the pump is frequently noisy. Not only that, I think the air in the system has put a strain on the pump and I have had to replace the pump three times in 5 years! I want to avoid this happening again! Any ideas?
I don't think the system has a leak (as it seems to hold pressure OK for ages) but air still seems to get in (perhaps through the frequent topping up with 'aerated' mains water containing dissolved air). Hopefully, my period of frequent topping up has come to an end with me completing the rennovation of our old house, but can I fit some sort of automatic air bleed valve that will take out any extraneous air to make the pump (a) less noisy, and (b) last longer!?