Unbelievably loud banging from pipes

[Sam4]

When the hot water is turned on (not running hot water just heating it) there is often an extremely loud banging noise that lasts a couple of minutes and sounds like a group of people are banging pots and pans on the pipes and the whole thing is going to explode. Is this air in the pipes or something? Its really loud and seems to happen about half an hour after the hot water has been on. Will bleeding the radiators help?

 

[gas4you]

banging noises are usually to do with a lack of flow through the boiler, be it the pump knackered, sludge build up or a blockage of some other sort.

Does it do it with the rads on?

 

[JohnD]

what sort of boiler, how old is it.

 

[Softus]

Could be lots of things, e.g.:

1. Faulty cylinder thermostat;
2. Faulty MZV;
3. Faulty boiler thermostat;
4. Lack of bypass;
5. Air in the primary circuit;
6. Empty F&E.

 

[namsag]

Most likely cause after half hour of being on is the boiler stat has gone, bet if you put heating on noise will not happen as quick and take about an hour or longer but will start banging eventually