DIY Doctor UK DIY Forums

Can anyone help with a problem of banging noises and poor heating on downstairs rads. I have a Baxi back boiler and it has started to make severe knocking from the pipes running to the h/w tank upstairs. Also the downstairs rads at the back of the house are just warm. There is no air in rads, spare pump makes no difference, connections tight on back boiler. Could it be the hot water tank leaking internally somehow? It bangs after approx half an hour as if it is getting air in or getting too hot in pipes to tank.

Sounds like over the years limescale has built up in the boiler and furred up the pipes, as the pipes fur up the pipe size decreases. The water struggles to get away from the boiler and the pipes and boiler heat-ex starts to bang or make a rumbling noise.

You can buy descaler from any plumbing shop. Add this to the system (follow instructions on bottle) once it has quietened down, it's best to drain and flush system and add a inhibitor to prevent it happening again.

Thanks for that, but the boiler is only 4 years old. The system is quite clean and has had inhibitor added for a number of years. I am wondering if a higher powered pump might push the water round better. I have eight rads.