How to Bleed Radiators and Towel Radiators (Step-by-Step Guide for UK Homes)

If your radiators feel cold at the top but warm at the bottom, or you can hear gurgling noises when the heating is on, it’s time to bleed your radiators. Trapped air stops hot water from circulating properly, which means your home takes longer to heat up and your boiler works harder than it should.

In this simple guide, I’ll show you exactly how to bleed radiators and towel radiators, what tools you need, and what to do if you notice ongoing pressure issues.

Why You Need to Bleed Radiators

Over time, air can build up inside your central heating system. This trapped air sits at the top of the radiator and prevents hot water from filling the whole panel.

Signs your radiators need bleeding:

• Radiator cold at the top, warm at the bottom
• Gurgling or bubbling noises
• Heating takes longer to warm up
• Some radiators not heating fully
• Higher energy bills than usual

Bleeding your radiators removes that trapped air and restores full heat output.

Tools You Need to Bleed a Radiator

Before you start, make sure you have:

• A radiator bleed key (or flathead screwdriver for some models)
• An old cloth or towel
• A small container or bowl
• Gloves (optional but recommended)

Radiator bleed keys are inexpensive and available from most DIY shops.

Important Safety Step – Make Sure Radiators Are Cool

This is crucial.

Always turn your heating off and allow radiators to cool down before bleeding them. Never attempt to bleed a radiator while it is hot.

Hot water can spray out under pressure and cause burns. Wait at least 30–60 minutes after turning the heating off to make sure everything is cool to the touch.

How to Bleed a Radiator (Standard Radiators)

Follow these steps carefully:

1. Turn Off the Heating

Switch off your central heating system and wait until radiators are completely cool.

2. Locate the Bleed Valve

The bleed valve is usually found at the top corner of the radiator. It looks like a small square or slot inside a round fitting.

3. Insert the Radiator Key

Place your cloth under the valve and hold your bowl underneath. Insert the radiator key into the bleed valve.

4. Turn Slowly Anti-Clockwise

Turn the key slowly (about a quarter turn). You should hear a hissing sound. This is the trapped air escaping.

Do not remove the valve completely. Just open it slightly.

5. Wait for Water

Once the hissing stops and water starts to come out in a steady stream, the air has been released.

6. Close the Valve

Turn the key clockwise to close the valve. Do not overtighten.

7. Wipe and Check

Clean up any water and move on to the next radiator.

How to Bleed a Towel Radiator

Bleeding a towel radiator works exactly the same way as a standard radiator.

The bleed valve is normally at the top of one side of the rail. Follow the same steps:

• Heating off
• Radiator cool
• Open valve slightly
• Release air
• Close once water flows

If your towel radiator is connected to both central heating and electric (dual fuel), make sure the electric element is switched off before bleeding.

After Bleeding – Check Boiler Pressure (Very Important)

After bleeding your radiators, you may notice the pressure on your boiler has dropped.

If you have a combi boiler, check the pressure gauge on the front. Most systems should sit between 1 and 1.5 bar when cold.

If the pressure is too low:

1. Locate the filling loop (usually a silver flexible hose under the boiler).
2. Slowly open the valves to let water into the system.
3. Watch the pressure gauge.
4. Close the valves once it reaches the correct pressure.
5. Do not overfill the system.

If you are unsure, check your boiler manual or contact a Gas Safe registered engineer.

What If You Have to Bleed Radiators Regularly?

If you find yourself bleeding radiators often, this is not normal.

Frequent air build-up can be a sign of:

1. A leak somewhere in the heating system
2. Low system pressure
3. Faulty expansion vessel
4. Corrosion inside the system

If your boiler pressure keeps dropping or you constantly need to top it up, seek a qualified plumber’s advice. Ignoring this can lead to bigger and more expensive problems.

How Often Should You Bleed Radiators?

For most UK homes, bleeding radiators once a year is enough. The best time is:

1. At the start of autumn before winter
2. If you notice cold spots
3. After any heating system work

Regular checks keep your heating efficient and reduce energy waste.

Final Tips for Best Results

Always start with the radiator furthest from the boiler.

Work through the house one radiator at a time.

Check boiler pressure after finishing all radiators.

Never bleed a hot radiator.

Bleeding radiators and bathroom radiators is one of the easiest home maintenance jobs you can do yourself. It improves heating performance, reduces energy costs, and helps your boiler last longer.

If you are unsure at any stage, or notice pressure drops and leaks, always contact a qualified heating engineer. It’s better to fix a small issue early than deal with a major repair later.

By following this guide on how to bleed radiators and towel radiators, you can keep your central heating system working efficiently all year round.

If your radiator still isn’t heating properly after bleeding, it may be time for a replacement. Browse our full range of modern, energy-efficient radiators.

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