How to Bleed a Radiator Step-by-Step Guide
Why Bleeding Your Radiator Matters
If your radiators are cold at the top but warm at the bottom, chances are they need bleeding. Over time, trapped air builds up inside radiators, reducing their efficiency. Not only does this leave rooms colder than they should be, but it also makes your boiler work harder, which means higher energy bills and unnecessary strain on your heating system.
Bleeding your radiators is quick, simple, and something every homeowner should know. Done right, it can:
Restore full heat output
Lower your energy costs
Extend the lifespan of your heating system
Keep your home cosy during autumn and winter
Tools You’ll Need Before You Start
A radiator key (or flat-head screwdriver for some modern models)
A cloth or small towel
A container or jug to catch drips
Heating system turned on beforehand, then switched off before bleeding
Pro tip: If you don’t already have a radiator key, they cost less than £5 and are available in most DIY stores or online.
Step-by-Step Guide to Bleeding Your Radiator
1. Turn Your Heating On
Run your central heating until all radiators are fully hot. This pushes air pockets to the top, making them easier to release.
2. Switch Heating Off and Let It Cool
Never bleed radiators while the heating is still running, hot water can scald. Let them cool slightly for safety.
3. Find the Bleed Valve
At the top of your radiator (usually on the side), you’ll see a small square or slot, that’s the bleed valve.
4. Insert the Radiator Key
Place your radiator key into the valve. Hold your cloth and jug underneath to catch any water that escapes.
5. Release the Air
Turn the key slowly anti-clockwise. You’ll hear a hissing sound as trapped air escapes. Keep turning until water (not air) starts to dribble out, then tighten the valve clockwise again.
6. Check Boiler Pressure
After bleeding, always check your boiler’s pressure gauge. If it has dropped below the recommended level (usually 1-2 bar), you may need to top it up via the filling loop.
7. Repeat if Necessary
Work your way around all radiators in your home, starting with the one furthest from your boiler and moving closer.
Common Mistakes to Avoid
Bleeding with heating on - dangerous and ineffective
Forgetting to protect walls and floors - water can stain
Not checking boiler pressure afterwards - can lead to heating breakdowns
Over-tightening the valve - can damage the fitting
How Our Guide Compares to Others
Not all radiator bleeding guides are created equal. Most competitors keep it short and skip important details, which can leave you with half-warm radiators and higher bills. Here’s how The Radiator Hub’s complete guide stacks up:
| Feature | Typical Competitor Blog | The Radiator Hub Guide |
|---|---|---|
| Step-by-step bleeding process | ✅ Basic steps only | ✅ Full process with safety checks |
| Boiler pressure check included | ❌ Often missed | ✅ Explained with filling loop guide |
| Common mistakes to avoid | ❌ Skipped | ✅ List of real world issues + fixes |
| Extra tools checklist | ❌ Not included | ✅ Full list (key, towel, jug, etc.) |
| When to call a professional | ❌ Rarely mentioned | ✅ Croston Plumbing & Heating |
When to Call a Professional
If your radiator stays cold even after bleeding, or your boiler pressure keeps dropping, there may be a bigger issue such as:
Sludge build-up inside the radiator
Pump circulation problems
Leaks in the system
At this stage, bleeding won’t solve the problem. You’ll need a professional heating engineer to diagnose and fix the issue.
👉 For expert help in Chorley, Preston, Leyland and across Lancashire, our sister company Croston Plumbing & Heating can help with radiator repairs, powerflushing, and boiler servicing.
Final Thoughts
Bleeding your radiators is one of the easiest home maintenance tasks you can do, and it pays off immediately. Warmer rooms, lower bills, and a more efficient heating system all from a 5 minute job.
Ready to make your home winter-ready? Shop our full range of designer radiators here at The Radiator Hub. Or, if you’d rather let the professionals handle it, get in touch with our sister company Croston Plumbing & Heating
FAQ's
Q: How often should I bleed my radiators?
A: At least once a year, ideally before winter.
Q: How long does it take to bleed a radiator?
A: Usually just 2-3 minutes per radiator.
Q: What happens if I don’t bleed my radiators?
A: Your heating will be less effective, bills may rise, and long-term damage can occur.
Q: Do I need to bleed every radiator in the house?
A: Yes, even if only one seems cold, air can travel through the system.
Q: Can bleeding a radiator save money?
A: Absolutely. A properly working radiator uses less energy to heat your home.