How to resolve common radiator problems yourself

Please note, we can only give you basic advice on this page to do the job yourself. Make sure you use the right tools and protective equipment to avoid hurting yourself or damaging your home. Always consult a professional for more complex repairs.

As we haven’t been using our radiators as much, it’s hard to know there’s a problem until you really need them, and with the cold weather setting in, it’s best to check sooner rather than later.

Below, we’ve listed some of the most common radiator problems and how to fix them yourself. However, if you’re not confident in what you’re doing, you should always contact a professional to repair faults for you.

Your radiators have cold spots

If the radiator is cold in spots but warm in others, this could still be down to trapped air, in which case you may need to bleed your radiators.

Remember: if you’re testing the temperature of a radiator, be careful if you’ve got the heat turned up. Use a cloth or towel to protect your hands.

Bleeding your radiators

You’ll need to turn your heating off and wait for the radiators to cool down before starting to bleed your radiators. The water inside the radiator may stay hot for some time, even after the heating is switched off.

Once you’re happy that your radiator is cold, you’ll need to make sure you have the right tools and protective equipment to complete the job. These include the radiator valve key (if you have older radiators) or a flat head screwdriver for newer models, along with a towel/container to catch any excess water.

1. Turn the key/screwdriver anti-clockwise to loosen the valve

2. Keep going until you can hear a hissing sound – this is the air escaping

3. Wait until the hissing noise stops

4. Once water begins coming from the valve, turn the key/screwdriver clockwise to tighten it again

5. You can now test the radiator by turning your heating back on and checking for cold spots

Top Tip: It’s best to bleed your radiators once a year, ideally before you start using them frequently (around September/October time)

One radiator takes longer to heat up than the others

If you’ve turned up your thermostat but one radiator is colder than the rest, it’s likely that trapped air is the cause. It’s possible that the hot water from your boiler isn’t being evenly distributed and that you’ll need to balance your radiators.

As above, you’ll need the right equipment to work effectively and safely. This includes your radiator key/flat head screwdriver, a valve key or spanner and a digital thermometer.

Make sure you switch off your heating before starting this exercise as they’ll all need to be completely cold.

1. Open the radiator valves by turning them anti-clockwise

2. Turn your heating on and make a note of how quickly each radiator heats up. The radiators nearest the boiler tend to heat up first

3. Turn your heating off again and once completely cooled, switch it back on

4. Close the valve on the fastest radiator first, then open it a quarter and take temperature readings. You’ll need to measure the temperature of the pipework next to the valve first and then the temperature of the pipework on the opposite side. Make a note of both readings and slowly open the valve until the difference in temperature between the two pipes is 12°C.

IMPORTANT: This exercise can take time to complete as you have to wait for the temperature of the radiator to change each time you adjust the valve.

1. You’ll need to repeat this for each of your radiators in the order they took to heat up. You may find that the amount the valve needs to be opened relates to the distance from the boiler it is.

You shouldn’t need to balance your radiators often, but it’s good to get into the habit of checking that they are heating up at the same time and repeat the above if not.

If you’ve recently done any of the below, you may need to balance your radiators:

• Replaced your boiler/altered your heating system

• Removed your radiators for decorating

• Flushed your central heating system

Your radiator is continually not heating up

If you’ve bled your radiator but it’s still not heating up properly or taking much longer than expected to heat up, you may have a build-up of debris in the radiator. This could happen due to several different reasons:

• You live in a hard water area – this will cause limescale to build-up in your radiators, similar to a kettle

• Your radiator is rusting

• If your central heating system is corroding internally, black sludge can form

Unblocking your radiator(s)

Unfortunately, to unblock your radiator, this will need to be completely removed and taken somewhere else to clean. You may want to speak to a qualified engineer at this point who can:

1. Bleed the radiator if you haven’t already

2. Remove the radiator (with the valve closed) and take it outside

3. Use a hose to spray out any dirt

4. Reattach the radiator once it’s flushed out and dried

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