2. Boiler is making noises (gurgling, whistling or banging)
If your boiler is making vibrating, banging, gurgling or whistling noises, the most likely cause is air in the system. Low water pressure or a failing pump could also be the cause. If you hear a noise coming from the boiler or heating system, don't ignore it as there's probably a fault. The potential fault will vary depending on the type of sound and where it's coming from.
What you can do
Adjust the settings or check the connectors if your boiler is humming or vibrating. The noise could be a symptom of a more serious fault, so if you're not sure make sure you contact your supplier.
Bleeding your radiators can help if the pipes are gurgling. However, a frozen condensate pipe can also cause a similar noise (see number nine below).
Knocking can be caused by the expansion and contraction of your heating pipes. This is normal, but it could be useful to check that the pipes aren't fixed to floorboards or joists too tightly.