By AJ, certified Gas Safe engineer and lead plumber at 247 Emergency Plumbers Edinburgh · Checked
Gurgling radiators usually have trapped air and need bleeding. Ticking and creaking when the heating comes on or goes off is normal: the metal expands and contracts. Banging usually starts at the boiler, from sludge or scale restricting the flow, and needs an engineer.
Quick guide: cold at the top means air (bleed it). Cold at the bottom means sludge (needs flushing). Cold all over while others are hot usually means a stuck valve.
What it could be and what to do
Gurgling You may be able to fix this
Likely cause: Viessmann says gurgling is air trapped in the system, which often leaves the radiator cold at the top.
What to do: Turn the heating off, let it cool and bleed the radiator. Check the boiler pressure afterwards.
Ticking, clicking or creaking You may be able to fix this
Likely cause: The metal of the radiator and pipes expands as it heats up and contracts as it cools. Viessmann says this is normal.
What to do: Nothing to fix if it only happens when the heating comes on or goes off. If pipes knock constantly, they may be loose under the floor and need clipping.
Banging Engineer needed
Likely cause: Viessmann says banging is usually kettling at the boiler, caused by scale or debris restricting flow, even though you hear it in the radiators. Most water in Scotland is soft, so in Edinburgh sludge is often more likely than limescale.
What to do: Book a Gas Safe engineer. The system may need flushing or a boiler part replacing. See our page on boiler noises too.
Safe radiator checks you can do
These are the checks we suggest without an engineer. Never open the boiler casing.
Heating off first: turn the heating off and let radiators cool before you bleed them or touch a valve. The water can scald.
Feel the radiator: with the heating on, note whether it is cold at the top, the bottom or all over. That tells you which page above to use.
Valves open: check the thermostatic valve is turned up and the lockshield at the other end is not closed.
Bleed: open the bleed valve slightly with a radiator key, catch the water and close it when water flows steadily.
Pressure: after bleeding, check the boiler gauge shows about 1 to 1.5 bar when cold, and top up as your manual shows. Low boiler pressure guide →
Radiator still cold or leaking? We can sort it.
Our callout is from £75 in standard hours (out of hours £100–£180) for attendance and diagnosis. Repair labour and any parts are agreed with you before work starts.
Our emergency line is open 24 hours a day, 7 days a week.
Every heating system is different. This page is general guidance, not a diagnosis.
YOUR QUESTIONS, ANSWERED
Helpful answers before you call.
Why are my radiators gurgling?
Gurgling usually means trapped air. Turn the heating off, let it cool and bleed the radiators, then check the boiler pressure is about 1 to 1.5 bar.
Is it normal for radiators to tick?
Yes. Ticking and creaking when the heating comes on or goes off is the metal expanding and contracting. It is not a fault.
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