When my boiler turns off with the stat having reached its desired temp, after a minute or so there is a very audible sound of water rushing into the pipes at the top of the boiler. Its as if there is air in the pipes which then at some point is filled with water. It doesn't do this everytime though the boiler switches off. Is this normal and if not, what can I check? Should the main feed and return pipes to the boiler have air vents on them?
If you have bled all the rads etc and there is no problems with air then its probably nothing to worry about.
It's air, and should not be there. There are sure to be air vents on the system, it's a case of finding them. Try bleeding air from these when the system is turned off ONLY. You don't say what boiler you have or if the system is sealed or not, so make sure the system is full/up to pressure befor you turn it back on. Failing this call in a Plumber/Heating enginer.
Thanks for the replies. The boiler is a wallstar in the wall boiler. The system is a vented type. I have had a look in the loft and have 3 pipes as part of the boiler system that have air vents on the top (manual type) I will try these and see if any air comes out.
if its after the pump stops it could just be the water coming back to the boiler if the boiler is lower than the pump