Diagnose central heating problems

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Central heating systems are very complex and this means that faults are not uncommon. If you notice that your radiators are cold in any part of your house, this can indicate a problem with the whole system.

If your central heating fails, don’t panic. There are plenty of steps you can take yourself before you call an engineer. If you are concerned about the cost of central heating repairs, you can purchase a central heating cover policy to put your mind at ease.

Remember that your central heating is very complex, involving gas, water and electrics. If you are uncomfortable or unsure at any stage of these checks, always call in a professional. Now, let’s explore the most common ways to diagnose a problem with your heating…

No heating?

Check the thermostat

It might sound obvious, but the first step is to check that the system is turned on and calling for heat. Some boilers feature an energy-saving cut out that will prevent the boiler from turning on when the thermostat has been set too low. The boiler will only work if the thermostat is set above room temperature. You should also check if your thermostat is battery powered as a low battery can result in inaccuracies.

Check the timer

If the power supply has been interrupted, this can lead to the timer resetting and preventing the boiler from turning on at the scheduled intervals. Check that the time matches the actual time and that you haven’t set the heat to turn on at 5 am instead of 5 pm.

Hit the reset button

If you have made any changes to the boiler settings or inputs, you may need to hit the reset button to get things started again. This will differ on all boilers, so check your manual to find out if you have a reset button and where this button is located.


Diagnosing radiator problems

Upstairs radiators are cold

If the radiators in the upper floors of your home are cold but the rest feel warm, this could mean that the feed and expansion cistern is empty. To fix this, you will need to locate the cistern, which is usually found in the loft in a small tank. Only venture into your loft if it is safe to do so, otherwise, contact an engineer to help.

To refill the cistern by yourself, locate the tank and tap the ball valve. This should prompt the inflow pipe to fill the tank and then shut off when there is enough water to float the ball valve. It’s important not to manually fill the tank, as this can lead to overfilling and the water will not have enough room to expand.

Once you’ve filled the cistern, the affected radiators will need to be bled. This should resume heating in the upper rooms. After a few days, check the levels in the tank. If the ball valve is faulty again, you will need to call an engineer.

Downstairs radiators are cold

When your downstairs radiators fail to heat up, this can be the result of an airlock in the system. Turn off your upstairs radiators completely and see if this allows your downstairs radiators to heat up. If this is the case, you’ll need to call a heating engineer to fix the problem.

It’s vital to fix faulty radiators quickly in the winter as cold radiators can lead to frozen and burst pipes which can be very costly to fix and also cause a lot of damage in your home.

Cold patches on the radiator

This is often the result of air in the central heating system. You’ll need to bleed the radiator to release the trapped air. You can do this yourself, or you can call an engineer if you don’t have the tools or mobility to manage this.

Middle of the radiator is cold

When the middle of your radiator is cold, this is often the result of a sludge build up inside the radiator which is preventing the flow of water. While some people might be comfortable handling the DIY method of fixing this, it’s better to call in the professionals. Removing build up from radiators is a messy job that is best left to the professionals.

How to deal with airlocks

When you have air in your central heating system, it can reduce the efficacy of the whole system. If the problem radiator seems to move around your home, this is usually the result of airlocks. The first step to solving this is to bleed your system and see if this resolves the problem. If bleeding the radiators doesn’t solve it, you’ll need to call in the experts.

Adjust the valves

If it’s the radiator closest to the boiler that heats up the most and then the rest stay warm or cold, you can distribute the heat more evenly by closing the lockshield slightly. This will ensure more hot water moves to the radiators further away. This is another task best left to the experts, as you might misdiagnose a heating problem.


Use thermometers

Sometimes, you need to make adjustments to each individual radiator to ensure the whole system is working efficiently. Using radiator thermometers, start with the radiator that heats up first. Close the lockshield valve, place a thermometer at each end of the radiator and then slowly open the valve until the reading is the same at each end. Do this for every radiator in your house in the order they heat up.

Deal with leaking pipes

It might seem like a disaster, but you might be able to deal with a leaking radiator yourself. A pinhole leak is often the result of corrosion inside the radiator. This can even happen to brand new installations if debris created during installation isn’t correctly removed.

To deal with this, a plumber will carry out the following steps:

  1. Turn off your boiler and let it cool down
  2. Place a dust sheet and bucket under the leak
  3. Turn off the valves at both ends of the radiator
  4. Drain the radiator
  5. Remove the radiator, leaving the rest of the system intact
  6. Use a non-acidic cleaner to flush out the system
  7. Refit the radiator

Problems with leaky pipes

A small leak can quickly become a big leak if left unchecked. Always deal with leaky pipes as soon as you notice them.

Check for leaky connections and joints – You might simply need to tighten a joint using a spanner or wrench. If the joint has been soldered, the entire thing will need to be replaced.

Leaking from a pipe – If there is no joint or connection, you’ll need to replace the whole pipe. A short term solution is to use a special sealant to prevent water damage while you wait for a professional. A rag around the joint will also keep a small leak at bay.

Problems with noisy boilers

If your boiler makes bangs, bumps and clanks, this is usually a sign that the system doesn’t have enough water. As outlined above, you should only access the feed and expansion tank if you are confident. You may also need to repressurise the system once the tank has been filled. Check your individual boiler settings, but most will need to be at minimum 1 bar.

Loud noises can also be the result of residue build up or air. This is something that should be tackled by a heating engineer.

If the water is making a gurgling sound, this is usually a sign you have air in the system. Your heating should be quiet when it turns on. You may need to bleed your radiators to solve this common problem.

Can Central Heating Problems Be Caused by Asbestos in the Home?

If you are experiencing central heating problems, it’s important to consider the possibility of finding asbestos in your home. Asbestos was commonly used in insulation around heating systems, and when disturbed, it can release dangerous fibers. It’s crucial to address any potential asbestos issues for the safety of your home.

Can Central Heating Problems Be Fixed Without Switching to an Oil Heating System?

Yes, many central heating problems can be fixed without switching to an oil heating system. While there may be some benefits to using an oil heating system, it’s not always necessary to make the switch. With proper maintenance and repairs, central heating systems can continue to operate efficiently for many years.

Safety first!

When dealing with boilers and central heating systems, you should never attempt to open or service your boiler as this can be very dangerous. If you aren’t sure how to fix a problem, always call for the help of a registered, GasSafe engineer.


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