white radiator on orange background

Radiator Troubleshooting Advice

  • 1 min read

Written by Domestic & General

Because radiators aren’t always in use throughout the year, you can’t always tell if they’re working as well as they should until you really need them. This can be hugely inconvenient, as well as potentially making your home cold when temperatures drop. If you find yourself in this situation, it’s handy to have a guide to find the problem and deal with it, or know when it’s time to call a boiler engineer.

In this article, we’re going to answer some commonly asked questions to help you with your central heating problems. However, some of our advice does include hands-on maintenance. If in any doubt, it’s advisable to contact a professional to repair any faults.

What Do You Do if One Radiator is Cold?

Firstly, is your central heating switched on? After summer, it’s an easy thing to overlook, so check this first.

If you’ve turned up your thermostat and made sure all your radiators are switched on, this is a great way of checking for a localised problem. By working this out at an early stage, it can mean saving a lot of time looking for problems elsewhere, such as the whole radiator system or the boiler.

Why Would One Radiator Stop Working?

hand turning a thermostat on

If one, or sometimes two, radiators aren’t heating up, it’s highly likely that trapped air is the cause. While radiators are out of use in warmer months, air can get trapped through small leaks or through the pump above the supply pipe.

If you find the radiator is cold at the bottom yet warm at the top, trapped air can also be responsible, however, there might also be debris blocking the heat – more on this later in this article. If you’re testing the heat of the radiator, be careful, especially when the heat is turned up, in case of potential burning. Use a cloth to protect your hands.

How do You Remove Air From a Radiator?

If you’ve identified which radiator isn’t functioning properly, and it’s possible that there is trapped air, it’s best to bleed the air out. Bleeding a radiator is a fairly simple process and perhaps takes the least amount of time (or potential cost).

Can You Bleed a Radiator When the Heating is On?

turning radiator valve with cup underneath

Make sure the central heating is turned off when bleeding a radiator. Also, if the heating has been on, leave the radiator for long enough for them to be completely cooled down. The water inside the radiator may still be hot, even scalding, for a little while after the heating is switched off.

How to bleed a radiator:

There are two ways of bleeding a radiator, depending on its age, which means adjusting the valve. This is the part that usually has a plastic cap. For older radiators, a radiator valve key is needed. It’s probably in that one kitchen draw with the bottle openers and candles! If you can’t find one, you can buy them fairly cheaply from hardware and DIY stores. For newer radiators, a flat head screwdriver will work.

  1. Before starting, keep a towel handy as water may start running from the valve. The radiator valve is usually found on one particular side.
  2. Turn the key, or screwdriver, anticlockwise to loosen the valve.
  3. Keep going until you hear the hiss of escaping air.
  4. Leave the valve open until the sound of the air being released stops.
  5. When water begins to trickle from the valve, start to turn the key or screwdriver clockwise to tighten it.
  6. The radiator should now be bled, which you can test by putting the heating back on.

What are the Signs of a Clogged Radiator?

hand on the top of a radiator

Continual problems with a radiator not heating up properly might be down to a build-up of debris in the radiator itself. A clogged radiator can show the same sort of problems that a radiator with trapped air might such as having cold spots or not warming up at all.

How do you Unblock a Radiator?

The process of unblocking a radiator means completely removing it and taking it somewhere to be cleaned out, either in a garden or yard (or outside on the front steps if you have understanding neighbours).

Before starting, turn off the central heating and wait for it to cool down completely, as with bleeding the radiator. Because there’s a likelihood of mess from a build-up of dirt inside the radiator, as well as water, put down towels and cloths under the radiator and around the pipes. It’s also a good idea to put a bucket under the radiator valve.

  1. Close the valve using an adjustable wrench by turning clockwise around the valve nut. However, it’s important to take note of the number of turns when closing the valve, as you will need to turn the nut by the same number when putting the radiator back.
  2. If you haven’t already, make sure to bleed the radiator using the process above.
  3. With the valve closed, remove the radiator, and take it outside.
  4. The most effective way of flushing a radiator is to use a hose to spray out all the dirt, which is mostly traces of rust, scale and dirt build-up. If you need to, you can also tap the radiator to loosen more dirt. Try to use something soft, so as not to dent or damage the radiator itself, such as a wooden mallet wrapped in a towel.
  5. With the radiator flushed out, and dried, you can reattach it.

Why are My Downstairs Radiators Not Working?

boiler with pipes linking to a radiator

Again, if you’ve checked the central heating has been turned on and you have little or no heating, this will need further investigation. If you’ve found that more than one radiator isn’t coming on, there are other areas to look into.

  • Central heating pump – Radiators above the ground floor tend to be closest to the boiler. Because of this, these radiators will often get hot water pumped to them first. If the heat isn’t travelling far from its source, and not warming other radiators (especially on a lower floor), it’s likely to be down to the central heating pump. The pump can be adjusted to increase the pressure, but if the problem persists, it might be time to call out an engineer.
  • Diverter Valve – With some hot water systems, if hot water from a tap is running, a diverter valve will take the water from the heating to the tap. If the hot water is running from the taps, but you’re getting no heat from your radiators at any point, it’s possible that the valve my be stuck in one position. Again, a job for an engineer.

We hope this has helped with troubleshooting to avoid unnecessary call outs. If problems persist, this could be down to some other issues with your boiler or controls, and it might be time to contact a heating professional.