Loud bangs from boiler after draining system - closed valve?

[steph]

Hi

I drained my system today as I was trying (and failed) to install new radiator valves. I have just switched the heating on this evening and the boiler suddenly made loud bangs so i hurriedly switched the heating off.

There are 2 valves in the loft, one which turned off the water in the bathroom and the other didn't seem to do anything. This valve that didn't seem to do anything has started leaking now so I have had to leave it closed, and I am guessing that it is connected to the boiler somehow causing the bangs?

 

[Darren Jackson]

Hard to say what the valves do without seeing them and tracing the pipeline. But it sounds like you have not vented the boiler or the pipes corectly. And air is trapped in the boiler and turning into steam thus kettling and causing the banging noise. The problem is you will need a Gas Safe engineer to vent the boiler properly as it will involve working on the boiler itself. Which is against the law unless you are a GSR engineer.

 

[steph]

aah yes i didnt vent oops! Amateur mistake. Do i need to drain again to do that or can i just go round the radiators?

 

[Darren Jackson]

Try bleeding all the radiators, the pump ( but only if it is not a fixed head inside a boiler) and any air vents elsewhere you can find, like maybe in the cylinder cupboard and loft space. The valve you have left closed in the loft because it has started leaking, it probably needs the gland tightening up to stop it from leaking and it also needs to be turned back on, as it sounds like it may be the gravity feed for your heating system.