How to Bleed Your Radiators Before Winter

If your radiators are hot at the bottom but cold at the top, there's air trapped in the system. Bleeding them takes 10 minutes and will make your heating work properly again.

Signs You Need to Bleed Your Radiators

• Cold patches at the top - The classic sign
• Gurgling noises - Air moving through the system
• Radiators taking ages to heat up - Especially after summer
• Some radiators not working - While others are fine

What You'll Need

• Radiator bleed key (about £2 from any hardware shop)
• Old cloth or towel
• Small container to catch water

That's it. No plumber required.

Step-by-Step: Bleeding Your Radiators

Step 1: Turn On Your Heating

Run your heating for about 15 minutes so radiators are warm. This builds pressure and makes the air easier to expel.

Step 2: Turn Off the Heating

Once warm, turn the heating off and wait 5 minutes for the water to stop circulating. This prevents hot water spraying when you open the valve.

Step 3: Find the Bleed Valve

Look at the top corner of your radiator - usually the side opposite the thermostatic valve. You'll see a small square fitting. That's the bleed valve.

Step 4: Prepare for Water

Hold your cloth under the valve and have your container ready. Some water will come out - not much, but enough to stain a carpet.

Step 5: Open the Valve

Insert your bleed key and turn anti-clockwise. You'll hear a hissing sound - that's the trapped air escaping.

Don't unscrew it fully. A quarter turn is usually enough.

Step 6: Wait for Water

Keep the valve open until the hissing stops and water starts to dribble out. This means all the air is gone.

Step 7: Close the Valve

Turn the key clockwise to close. Don't overtighten - just until it's snug.

Step 8: Repeat for All Radiators

Work through your house, starting with the ground floor and working up. Radiators furthest from the boiler usually have the most trapped air.

Step 9: Check Your Boiler Pressure

After bleeding, check your boiler pressure gauge. It should read between 1 and 1.5 bar when cold. If it's dropped below 1, you'll need to top up the system (repressurise).

How to Top Up Boiler Pressure

Most combi boilers have a filling loop - a braided silver hose under the boiler with one or two valves.

1. Locate the filling loop
2. Open the valves slowly (one or both, depending on system)
3. Watch the pressure gauge rise
4. Stop at 1.2-1.5 bar
5. Close the valves

If you're not sure, check your boiler manual or give us a call.

When to Bleed Your Radiators

Good times to check:

• Before winter - Get your heating ready for the cold months (see our winter maintenance checklist)
• After the heating's been off all summer - Air accumulates over time
• If you notice cold spots - Don't ignore them
• After any plumbing work - Air often gets into the system

When to Call a Professional

Bleeding radiators is simple, but call a pro if:

• Pressure keeps dropping - You might have a leak somewhere
• You have to bleed constantly - Something's wrong with the system
• Water is discoloured - System might need a powerflush
• Radiators are still cold after bleeding - Could be a pump issue or blockage

Quick Tips

• Bleed radiators in order: ground floor first, top floor last
• If you don't have a bleed key, a flat-head screwdriver sometimes works on modern valves
• Brown water is normal (it's rust from the system) - just have your cloth ready
• Do this yearly as part of your autumn maintenance

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Want us to handle it? We service heating systems across Exeter and can bleed radiators, check your system, and top up pressure. Call 01392 964094 or get a quote.