I have recently had a new valliant eco plus gas boiler fitted, along with 13 new lockshield valves and TRV's on all the radiators. The central heating was fitted in 1987. The system has been power flushed but their is a problem with an airlock. When the central heating is switched on it takes 4 hours and the radiators are all collecting air and water begins to run out of the overflow pipe into the garden from the header tank. I am constantly bleeding air 3 times aday and air reaccumulates constantly. The boiler cuts out onto anti-cycling mode.THe installer now wants to change the pipe work upstairs but does not know which pipe to change!!How do you remove an airlock without changing pipe work. The central heating worked fine until I had a new boiler fitted.

Mary Rich, June 2010

Just get that cold feed blanked off, if it is visable and get at able within the boiler region or if it passes thro' the airing cupboard just put a plastic cap on it and divert the pipe coming from the F&E and have it put in next to the vent line but not between the vent and the pump remember no more that 150mm away from each other.Feedback result for interest.If cap(plastic) is possible at boiler it has to be at least 1mtr away from boiler it would be easier to fit an inline valve at this stage then cap it later.

Guytawe, June 2010

Thanks for your help. The valliant boiler is an open vent system. Air is being sucked in down the vent pipe that sits over the header tank in the loft. The airing cupboard is very noisy with gurgling air around the pipes.
Do you know the name of a good plumber in the Berkshire area that can diagnose problems without too much mess in going under bedroom carpets and floor boards?
The pump sits by the hot water cyclinder in the airing cupboard and I can see the vent pipe that sits on the inlet side of the pump.The cold feed pipe goes to the boiler down stairs in the kitchen.
I have been told there is possibly an air block in the return pipe!! Help!!!!!!!!!!!

Mary Rich, June 2010

Initally I'd like to think that the correct Vaillant model was fitted which should be the Eco plus Open Vent if that is correct then the answer may be that the vent pipe and the F&E cold feed are not at a balanced point in the system.These two pipes should be close together no more than 150mm apart preferrably on the inlet side of the pump this would then give a positive pressure throughout the system thereby not drawing in any air from v/v glands etc.Having them on the discharge of the pump will work but is not ideal.

Guytawe, June 2010