Radiator noises can be annoying, but they’re also a useful clue that something in your heating system needs attention. Homeowners in places like Bordon, Whitehill, Liphook, Alton, and Farnham often report radiator banging at the start of the heating season, but the good news is that many causes are simple to diagnose and even easier to fix.
Understanding radiator banging
The term radiator banging usually describes a sharp knock or dull thud coming from the radiator itself or from pipework leading to it. The noise may happen when the heating first comes on, when radiators warm up or cool down, or randomly during the heating cycle. While it can sound alarming, most causes are straightforward and safe to investigate as a homeowner.
Quick checks you can do now
Before you call an engineer, there are a few simple checks you can carry out. These checks don’t require tools or heating knowledge and are safe for any homeowner.
- Check whether the radiator valves are fully open or partially closed.
- Listen for gurgling sounds that may indicate trapped air.
- Feel for cold spots that could point to sludge build-up.
- Check if pipework is touching walls, floors, or brackets.
- Make sure your boiler pressure is within the recommended range.
These quick checks often help you identify the source of the problem before moving on to more detailed troubleshooting.
Common causes of radiator banging
Several factors can cause your radiators to bang, and thankfully most of them are easy to fix once identified. Below are the most common reasons.
1. Trapped air in the system
One of the biggest culprits for radiator banging is trapped air. Air pockets can move through your pipework and create knocking or tapping sounds, especially when water flow changes rapidly. Residents around GU35 and GU34 often notice this early in winter after their heating has been off for a few months.
2. Sludge and debris buildup
Over time, rust and mineral deposits collect inside radiators and pipes. This sludge can disrupt water flow, causing overheating in certain spots and uneven circulation. When hot water meets a blockage, expansion and contraction can cause banging noises.
3. Pipe expansion and contraction
As your heating system warms up, metal pipes naturally expand. If those pipes are fitted too tightly through joists or clipped too firmly to walls, the expansion movement can create loud bangs or taps. This is common in older homes in areas like Farnham and Alton.
4. High flow rates or pump speed
If your boiler or pump is pushing water too quickly through the system, radiators can bang as valves or pipes react to the increased pressure. This is especially noticeable if the noise starts shortly after a new boiler installation.
5. Partially closed radiator valves
Thermostatic radiator valves (TRVs) and lockshield valves need to be set correctly. A partially closed valve can restrict water flow, causing turbulence and noise within the radiator.
How to fix common radiator banging issues
Once you’ve identified the likely cause, there are several homeowner-friendly steps you can take to solve the problem.
Bleeding your radiators
If you hear gurgling or notice cold spots at the top of a radiator, trapped air is likely the cause. Bleeding a radiator releases this air.
- Turn the heating off.
- Use a radiator key to slowly open the bleed valve.
- Let the air escape until water flows steadily.
- Close the valve fully.
Once done, check your boiler pressure and top it up if needed.
Adjusting radiator valves
Make sure both valves on each radiator are open at least halfway. A fully closed lockshield valve, for instance, can make a radiator bang due to water forcing its way through too small an opening.
Balancing your heating system
If some radiators heat quickly while others stay lukewarm, balancing may be required. This involves adjusting lockshield valves throughout the home so hot water flows evenly. Homeowners in Bordon and Whitehill often notice improved performance after balancing, as many older homes have been extended or altered over the years.
Checking pipe brackets and clearances
If the banging is coming from beneath floors or along walls, expansion could be the problem. Check any visible pipework to make sure it isn’t tightly pressed against timber or metal. Gently adjusting pipe clips or adding cushioning can stop the noise.
Lowering pump or boiler flow speed
If banging started after work on your boiler or pump, it could be set too high. Most boilers allow adjustment of flow temperature or pump speed. Lowering this slightly can reduce pressure fluctuations and stop banging. If you’re unsure, leave this to a Gas Safe engineer.
Checklist: When you should stop and call a professional
Most radiator banging is harmless, but there are cases where professional help is the safest option. Use this quick checklist:
- The banging is very loud or sudden and you can’t find a simple cause.
- Your boiler pressure keeps dropping after bleeding radiators.
- Multiple radiators are affected even after trying basic fixes.
- You see leaks, corrosion, or damaged valves.
- Your system hasn’t been serviced in over a year.
When a Gas Safe engineer is essential
If the issue relates to boiler controls, circulation pumps, internal boiler pressure, or anything involving gas appliances, you must call a Gas Safe registered engineer. Engineers will carry out checks you can’t safely perform, such as verifying pump function, checking for system blockages, or testing boiler components.
Professionals can also perform a system cleanse or powerflush if sludge is the source of the banging. Homes around GU9 and surrounding areas often benefit from this after years of sediment buildup.
Preventing radiator banging in the future
Prevention is often easier than repair. A few simple maintenance habits will keep your heating running quietly and efficiently.
- Bleed radiators every autumn before the heating season starts.
- Have your boiler serviced annually by a Gas Safe engineer.
- Check boiler pressure monthly.
- Ensure radiators are fully open during system warm-up.
- Keep pipework accessible where possible.
With these steps, you’ll reduce the likelihood of radiator banging returning and keep your heating system performing well year-round.
For friendly, Gas Safe help with radiator banging or any heating issue, call us on (01420) 558993.