Radiators are an essential part of any central heating system. They allow heat to be distributed around your home efficiently. However, over time air can enter the system and form bubbles inside the radiators, reducing their efficiency. This is why it is important to bleed your radiators regularly to remove this trapped air and ensure they are working at maximum capacity. But how often should you be doing this?
What is bleeding a radiator?
Bleeding a radiator involves releasing any built-up air that may be trapped inside. Radiators have a valve at the top which allows you to let this air out. To bleed a radiator:
- Turn the heating off and allow the radiators to cool.
- Locate the bleed valve at the top of the radiator. This is usually on the side or at the end.
- Place a cloth or towel under the valve to catch any water that escapes.
- Using a radiator bleed key, turn the valve counter-clockwise slowly. You should hear a hissing sound as the air escapes.
- Once water starts to come out and the hissing sound stops, close the valve by turning it clockwise.
- Check the pressure gauge on your boiler and top up if needed.
Releasing trapped air helps improve circulation allowing more hot water to reach the radiator and heat your room efficiently.
How often should you bleed radiators?
There is no set rule on how frequently radiators need bleeding. How often you need to do this will depend on several factors:
1. Type of heating system
The type of central heating system you have affects how much air can build up.
Gravity-fed systems tend to need bleeding more often, as air rises naturally to the radiators. Bleeding them about once a month through the winter is recommended.
Sealed, pressurised systems are less prone to air build-up, so bleeding 2-3 times over the winter is usually sufficient.
2. Age and condition of radiators
Old or damaged radiators may let in more air over time. If your radiators are over 10 years old, or you notice leaks, bleed them more frequently – around once every 2-3 weeks.
3. Positioning of radiators
Radiators on upper floors will accumulate air faster, so need bleeding more regularly than those downstairs. Bleed upstairs radiators every 2-4 weeks.
4. Noise or cold spots
If you notice gurgling noises from your radiators or cold spots at the top, this indicates air trapped inside. Bleed any affected radiators right away.
5. After alterations to your system
Work on pipework, fixes to leaks, or installing new radiators can all cause air to enter the system. Bleed all radiators a few days after any alterations.
6. Before the heating season
Bleeding radiators at the start of autumn before you switch on heating is recommended. This removes any air that has built up over the warmer months.
Signs it’s time to bleed your radiators
As well as the regular bleeding outlined above, look out for these signs that indicate your radiators need attention:
- Noisy radiators – Hissing, gurgling or bubbling noises point to air trapped inside.
- Cold spots at the top – Cooler sections at the top of the radiator mean air has accumulated here.
- Rooms heating up slowly – If it takes a long time for rooms to get warm, air may be preventing efficient circulation.
- Low system pressure – This can be caused by air pockets forming. Check pressure gauges and top up boiler if needed after bleeding.
Bleeding radiators as soon as you notice these issues will restore proper operation.
How to prevent air entering your heating system
While regular bleeding gets rid of air, there are steps you can take to prevent it occurring in the first place:
- Fix any leaks in pipework or radiators – these allow air to be sucked in.
- Top up system pressure if low – maintain pressure between 1-2 bar.
- Install microbubble diffusers – these break down air into smaller bubbles that don’t block pipes.
- Use a magnetic filter – traps sludge so it can’t cause blockages leading to air entering.
- Insulate pipes well – prevents temperature changes causing contraction and expansion of pipes.
Following these tips minimises air in the system so radiators won’t need bleeding as often.
When to call a heating engineer
DIY radiator bleeding is straightforward in most homes. But call out a professional heating engineer if:
- You can’t locate or reach the radiator bleed valves.
- The valves are seized up and won’t turn.
- Bleeding doesn’t resolve the issues with air.
- There are leaks when bleeding.
- Pressure doesn’t increase after bleeding.
- You need to frequently top up pressure.
This indicates an underlying problem needing qualified attention. An engineer can inspect the heating system, identify issues and repair where needed.
Conclusion
Bleeding radiators is an easy maintenance task anyone can do themselves. While there’s no exact timeframe, a good guideline is:
- Bleed upstairs and problematic radiators every 2-4 weeks.
- Bleed all radiators monthly if on a gravity-fed system.
- Bleed radiators 2-3 times over winter if a sealed, pressurised system.
Increase frequency if you have older radiators or notice signs of air. Bleeding before the heating season and after any work on the system is also recommended. Following these tips will keep your radiators working efficiently all winter long.