When your central heating system is acting up, it can be frustrating—especially when the temperature drops outside. Understanding common central heating problems and knowing how to fix them can save you both time and money.
Let’s dive into the most common issues you might face and the steps you can take to fix them.
The 9 most common problems with your central heating system
1. Radiator cold patches
Cold patches in radiators are among the most frequent central heating problems.
These patches can occur in various parts of the radiator, like the top, bottom, or middle. Each issue often indicates a specific underlying cause.
- Cold on top
When a radiator is warm at the bottom but cold at the top, it’s typically due to trapped air. This air prevents hot water from reaching the upper part of the radiator.
- Cold at the bottom
Radiators that are cold at the bottom usually suffer from a build-up of rust, sludge, or limescale. This build-up obstructs water flow, making it hard for the radiator to heat evenly.
- Cold in the middle
When a radiator is cold in the middle, the problem often lies with sludge or rust. This situation is more challenging to handle than a simple blockage at the bottom.
How to fix the problem
- For radiators that are cold on top:
You’ll need to bleed the radiator. Make sure to switch off your heating system and use a radiator key to open the bleed valve. Once the trapped air escapes and water starts to drip, close the valve.
If you’re not familiar with bleeding radiators, read our full guide on how to bleed radiators step-by-step.
- For radiators that are cold at the bottom:
A blockage or sludge build-up likely requires a chemical flush or professional power-flushing to clear out excess air and debris.
For more detailed instructions, check out our comprehensive guide on why your radiator might be warm at the top but cold at the bottom and how to fix it
- For radiators that are cold in the middle:
Unlike radiators that are just cold at the bottom, this issue can be more challenging to tackle. A more intensive power-flushing treatment might be needed to clear the middle section effectively.
In this case, it's best to call in a professional heating engineer to safely remove the build-up.
2. Hot and cold radiators
If some radiators are hot while others remain cold, this is a common problem in central heating systems. It’s usually caused by uneven water distribution or blockages within the system.
Your central heating system might not be balanced properly, which could lead to inefficient heating and cold spots throughout your home.
Sometimes, radiators upstairs may stay cold due to low boiler pressure, while downstairs radiators could be affected by a malfunctioning pump.
How to fix the problem
Start by checking the pressure gauge on your boiler. If the pressure is low, increase it to the recommended level by following your boiler’s manufacturer’s instructions.
Next, ensure that all radiator valves are open and functioning correctly. If the pressure is normal and you’re still experiencing issues, it might be due to an unbalanced system or a blockage.
Balancing your radiators can help even out water flow and improve heating efficiency. For a step-by-step guide, check out our comprehensive guide on how to balance radiators.
3. Boiler making unusual sounds
When a boiler starts making strange sounds like banging, hissing, or whistling, it’s a clear indication that something isn’t right. These noises, often referred to as 'kettling,' typically suggest the presence of trapped air, low water pressure, or limescale build-up within your heating system.
Ignoring your noisy central heating system can lead to more severe damage or in extreme cases, overheating. Kettling not only disrupts your comfort but could also mean that your boiler is struggling to function efficiently, potentially increasing your energy bills.
How to fix the problem
Begin by turning off your boiler to prevent further damage. If you suspect trapped air, try venting the excess air from the system using the air bleed screw on your boiler.
If the noises persist, descaling the boiler may be necessary to eliminate limescale build-up.
For more details on diagnosing different boiler noises, read our full guide on why your boiler might be making a banging noise and how to fix the problem.
4. You have heating but no hot water
If your radiators are working fine but you have no hot water, it’s typically linked to a faulty valve, thermostat, or airlock within the system. Often, this problem is due to the motorised valve being stuck or malfunctioning, preventing the proper flow of hot water.
Alternatively, a faulty thermostat can cause the system to incorrectly regulate water temperature, leading to inconsistent hot water supply.
How to fix the problem
Check the thermostat settings and ensure it’s set to at least 60°C. Then, examine the motorised valve and try to move the manual lever to confirm it’s not stuck.
If the valve isn’t the issue, you may need to release trapped air from the hot water cylinder or call a professional heating and gas engineer to inspect further.
To troubleshoot more possible causes and fix the problem, see our full guide on reasons why you might have no hot water in the house.
5. No heating or hot water
Experiencing both no heating and no hot water is a sign of a significant central heating issue. This problem can stem from a variety of causes, such as a malfunctioning pump, a failed pilot light, or even frozen pipes.
Low boiler pressure is another frequent culprit, indicated by a low reading on your boiler’s pressure gauge. Without prompt action, these issues can escalate, causing prolonged discomfort and potentially expensive repairs.
How to fix the problem
Begin by checking whether your central heating system is switched on and all relevant circuit breakers are in working order. If the pilot light is out, relight it according to the manufacturer’s instructions.
You should also check the boiler’s pressure gauge; if the reading is too low, add more water to bring it up to the correct level.
If frozen pipes are suspected, gently thaw them out, following the instructions on our step-by-step guide to thawing frozen condensate pipes. For more complicated problems, consult a professional.
6. Radiator leak
A leaking radiator is a significant issue that can lead to water damage and inefficiency in your central heating system. The leak might be due to corrosion, a faulty valve, or a damaged joint.
Radiator leaks often start small but can quickly become a larger problem if not addressed. Even minor leaks can cause drops in system pressure, which affects your boiler and other radiators.
How to fix the problem
To fix a leaking radiator, you first need to identify the source of the leak. In most cases, leaks stem from valves, pipe joints, or rusted sections. If you have a leaky pipe joint, you can likely tighten it yourself and hopefully fix the problem.
For a step-by-step guide on what to do next, check out our full article on how to fix a leaking radiator. If the leak persists after initial repairs, consult a professional plumber to avoid further damage.
7. Overflow running non-stop
If your central heating system features an overflow running non-stop, this typically indicates a problem with the water feed from your tank. While combi boilers don’t encounter this issue because they don’t use a separate water tank, regular and system boilers rely on a tank usually located in the loft.
These tanks have a ball-cock mechanism to regulate the flow of water and prevent overflows. However, if the ball-cock becomes jammed, it can lead to continuous overflow.
How to fix the problem
To address this issue, you can attempt to un-jam the ball-cock manually. However, be cautious when working with water tanks, as they can be complex systems.
If you're not confident in handling this yourself or if the problem persists, it’s best to call in a professional. They have the expertise to resolve the issue safely and efficiently, ensuring that your system operates smoothly without the risk of further complications.
8. Boiler needs replacing
When your boiler constantly breaks down, makes unusual noises, or does not provide hot water and heating efficiently, it may be time to replace it.
Older boilers are more prone to frequent repairs and are usually less energy-efficient, which can significantly increase your energy bills.
While replacing a boiler is a considerable investment, it can save you money in the long run by reducing maintenance costs and improving energy efficiency.
9. Boiler pressure
Boiler pressure is vital for your central heating system to function properly. When the pressure is either too high or too low, it affects how efficiently your system operates.
Here’s a breakdown of both low and high-pressure scenarios:
- Low boiler pressure:
Low boiler pressure can occur due to a leak, recently bled radiators, or even natural fluctuations in the system. When the pressure drops too low, the boiler won’t be able to circulate hot water effectively, leading to cold radiators and inconsistent water temperatures. Low pressure is a common problem, but if left unresolved, it can cause the boiler to shut down altogether.
- High boiler pressure:
On the other hand, high boiler pressure might be the result of a closed or faulty pressure relief valve or adding too much water to the system. High pressure strains the boiler and other parts of the system, leading to potential leaks or even damage to the boiler.
How to fix the problem
- When the boiler's pressure gauge is low:
Repressurising your boiler is usually straightforward. Locate the filling loop on your boiler and follow the manufacturer’s instructions to add more water until the gauge reaches the recommended level. Be sure not to overfill, as this can lead to high pressure.
- When the boiler's pressure gauge is high:
Turn off the boiler and carefully release excess pressure by bleeding the radiators. Check the pressure gauge frequently to ensure it falls within the correct range.
If the pressure remains high, it could be due to a faulty pressure relief valve, which a professional heating engineer should inspect.
For more tips on how to reduce boiler pressure, read our full blog.
When to call in a JustFix professional
While some minor issues can be resolved with DIY fixes, other problems need a professional touch.
Our team of Fixers works nationwide, ensuring you have access to skilled professionals at fair, fixed prices.
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When you book with JustFix online, we’ll connect you with a local heating and gas engineer who can assess and resolve your heating issues at a time that’s convenient for you. We ensure that all our Fixers are fully qualified and experienced in working with central heating systems, giving you peace of mind.
