Bleeding a radiator: the Guide

If your radiators make strange noises or don't heat up sufficiently, it's probably because air has accumulated inside them. To remedy this: it's time to bleed them. Here's how to do it.

Why bleed your radiators?

Bleeding a radiator removes the air that has accumulated inside it (for various reasons). This air prevents the radiator from working properly. By doing this :

• You save energy: A radiator containing air heats less efficiently and consumes more energy.
• Improve your thermal comfort If you bleed your radiators regularly, your home will be perfectly heated (there will be no uneven heating between rooms).
• Extend the life of your heating network Air in the circuit can damage your heating system in the long term (through a phenomenon known as "air leakage"). corrosion).
• Finally, you eliminate all unpleasant noises Air bubbles often cause rattling or gurgling noises in the pipes. By purging your radiators, these noises disappear instantly.

When should you bleed your radiators in Luxembourg?

There are several possible scenarios

• If you encounter a problem : If your radiators are making noise, not heating properly or showing temperature differences between the top and bottom, then it's time to bleed them.
• After work on the network : If you have removed or added a radiator (or carried out any other operation on the heating pipes), then air has most probably entered the system. This needs to be evacuated.
• Every year, before you turn on your heating for the winter (so in September or October, depending on temperatures). An annual purge is recommended to maintain the efficiency of your heating system.

The necessary equipment

To bleed your radiators in Luxembourg, you'll need a few simple tools:

• A purge key It is available in all hardware and DIY shops in Luxembourg, or can be ordered online.
• A container A small bucket or basin to catch any water that runs off (to avoid it falling on the floor and damaging your floor coverings).
• A cloth or towel To wipe up any water splashes.
• A pair of pliers or a screwdriver For certain types of radiator that do not require a special spanner (usually a flathead screwdriver).

For older radiators, particularly the cast-iron models still found in some Luxembourg homes, check the type of trap before buying your equipment. Some models require special tools (such as a hexagonal key, for example).

How to bleed a radiator, step by step

1. Prepare your radiators

• Turn off your heating or set your boiler to the "summer" position to stop water circulation.
• Wait until the radiators are completely cool (about an hour or two) to avoid any risk of burns.
• Fully open the thermostatic valves on all your radiators.

Your radiators are now ready to be vented.

2. Purge them

1. Start with the lowest radiator If your home has several floors, start on the ground floor and work your way up. The idea is to finish at the highest point (whether it's an upper floor or a vertical radiator - because air rises. You need to get rid of what's stuck at the bottom first).
2. Locate the air vent: It's usually at the top of the radiator, opposite the thermostatic valve. It looks like a small screw surrounded by a white or metallic outline. Some need to be unscrewed with a screwdriver, others can be unscrewed by hand.
3. Place your container under the trap to catch any water that runs off.
4. Use your purge key Insert it and turn it gently anti-clockwise (to the left). Or use your hand if you don't need a tool (this is the case for old cast iron radiators).
5. Listen to the air escaping You'll hear a whistling sound interspersed with a "glou glou", a sign that the air is rising to escape from the radiator. Above all, don't unscrew it all the way!
6. Wait for the water to run out When water starts to flow regularly, without air bubbles, this means that all the air has been evacuated.
7. Close the steam trap Turn the key clockwise. Do not overtighten to avoid damaging the mechanism.

Once all the radiators have been drained, turn your heating back on or put your boiler back into normal mode. So remember to check that all your radiators are heating properly and evenly after a few hours' operation.

Checking and adjusting pressure

After the operation, it is essential to check the pressure in your heating circuit:

1. Check the pressure gauge on your boiler (it indicates the pressure in the circuit). In Luxembourg, the recommended pressure is generally between 1.2 and 2 bar for most installations.
2. Adjust if necessary If the pressure is too low (less than 1 bar), you will need to add water to the circuit via the filler tap near the boiler.

If you notice a frequent drop in pressure after venting, this may indicate a leak in your system. In this case, it's best to consult a certified Luxembourg professional for a thorough diagnosis.

Problems that may be encountered after purging

The radiator is still not heating properly

If your radiator is still not heating properly, here are the possible causes:

• There is sludge in your heating circuit. These are deposits that have built up over time and are mainly composed of metal oxides resulting from pipe corrosion (this is a black deposit that can be removed, but will require professional descaling).
• Your defective thermostatic valve The valve that regulates the flow of water through the radiator may be damaged or blocked. If in doubt, have it inspected by a qualified plumber.
• There is too great a hydraulic imbalance in your network. If some radiators heat too much and others not enough, you may need to rebalance your installation.

Trap leaks

If it continues to drip after closing:

• Try tightening the trap slightly, without forcing it.
• If the leak persists, the trap seal is probably worn and needs replacing.
• If you need to change it, you can buy a new trap from any DIY shop and have it changed by a professional.

Good to know in Luxembourg: If you're looking to improve the quality of your heating and reduce your bills, you might be interested in a heat pump. Take a look at our dedicated guide to find out more.