Knocking on pipes when heating starts

[Gary Law]

Every time the heating comes on there is a knocking sound from the pipes that lasts 15-20 minutes, then intermittently while the heating is on. Only started over last 4 months. System / house 5 years old. Knocking/banging pipe noise always from same place. Why and what can be done?

 

[chris watkins]

Expansion of the pipe as they pass through something that is pinching them.
Most likely.

 

[Gary Law]

So, do I need a plumber or a joiner?

 

[chris watkins]

Heating engineer who can lift flooring would be my recommendation, Gary.

 

[Burger]

Every time the heating comes on there is a knocking sound from the pipes that lasts 15-20 minutes, then intermittently while the heating is on. Only started over last 4 months. System / house 5 years old. Knocking/banging pipe noise always from same place. Why and what can be done?

It could be trapped air/hydrogen build up (from sludge). Best getting a heating engineer.

 

[chris watkins]

It could be trapped air/hydrogen build up (from sludge). Best getting a heating engineer.

Not likely as this would effect the circulation through them & both normally accumulated in rads not pipes.

 

[Rob876]

Power flush the system and clip in the pipes, probably air in there somewhere.