Pipes banging

[selfbuildy]

When central heating is on when my pump is switched off by thermostat, loud banging comes from pipes.Doing my head in
When only hot water is called same happens
Please help

System is gravity fed with baxi back boiler. When central heating is called pump and boiler are called. When hot water is called only boiler energised.

 

[ChrisR]

When only hot water is called same happens

Nothing to do with the pump then, if you're right about when your pump comes on.

This is probably water boiling in the boiler, due to sludge and/or boiler scale. Old system/boiler?
When CH is on the pump keeps the boiler temp down but when the pump stops the residual heat in the boiler has nowhere to go so it gets hotter..

On HW the gravity flow will be low, so again the boiler gets hotter. Getting rid of the sludge/scale would help, as might turning the boiler temp down, or adding boiler silencer.

 

[selfbuildy]

Boiler is quite new,well under 10yrs.

Checked boiler, setting was on high, normally on 2-3!!!

Setting range on it is 1-4 then high.

Have turned down to 2 to see if it cures banging

Thanks for the reply Chris