Boiler makes a banging noise when finishing a cycle. Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Spanner]

Hi, got a problem with the boiler making a banging noise when it finishes it cycle. BGas say it's the water heater on the way out but won't replace until it finally gives up the go. They suggested adding some silencer to the system to see if it helps. Have some Fernox Silencer but not sure which tank in the loft to put it in? One is clear with a lot of sediment at the bottom and the other is a bluey colour, which is which?
Thanks, Spanner.

[plumbbob]

If the boiler is making the banging noise shortly after it has shut down, there is the possibility the pump overrun is not working.

Has anyone actually checked if the boiler requires an overrun and if it does is it happening?

[Spanner]

I have no idea if it needs one, the banging and clunking has only recently started happening when we had the cold spell. It does sound like the water is backing up. Take it the silencer would be a waste of money then, hpowever which tank is which in the loft?

[plumbbob]

hpowever which tank is which in the loft?

The little one is the heating tank. The big one supplies the taps.

I've got scant information to work on here, but if the clunking starts after the boiler switches off then it is most likely the water next to the heat exchanger is beginning to boil.

[Spanner]

Hi, both the tanks are an identical size, just one has clear water and the other is a bluey colour.
Is there anything the remidy the water boiling?

[plastic_man77]

From your point of view, the easiest way to tell which tank is which is to run the hot tap for a few minutes and then poke your head up the loft and see which one is filling. The one that is filling is for your hot water and the one that is not is for your heating.