How to Solve the 10 Most Common Problems with your Boiler

Our boilers are at the heart of our homes. Delivering hot water and warming rooms when needed, our boilers are essential to ensuring our homes are comfortable places to live in. But we tend to only pay them any mind when we’re either paying our energy bill or if something goes wrong.

A broken boiler can be a massive, and expensive, inconvenience, especially in the colder months when after long periods of inactivity, they’re forced back into use. Even if you have properly maintained and serviced your boiler, the large stresses placed on your central heating system can still cause them to fail.

Whether it’s a mechanical fault, general wear and tear or seasonal issues, there are a number of reasons our boilers become problematic or fail altogether, and they’re often difficult to diagnose without professional help. We’ve rounded up the 10 most common problems you might experience with your boiler, what might be causing them and what you can do to fix them.

No Heat or Hot water from Your Boiler

There could be a variety of things causing your heating system to lose heat, such as airlocks, broken diaphragms, low water levels, issues with the thermostat or the failure of motorised valves.

If you find that there’s no heat or hot water, the first place you should check is your boiler, specifically your boiler pressure and whether your thermostat is working correctly. Low boiler pressure is a frequent cause of central heating system malfunction and is something that is relatively easy to diagnose and rectify, which we’ll expound more upon below.

If you can’t see the problem yourself, or think you might have a more complex issue like a motorised valve failure, you will most likely need to call out an engineer to diagnose and treat the problem, whether it’s replacing faulty parts or broken electrics.

It’s vital that you only use Gas Safe Registered engineers, as they are regularly checked and certified by the UK’s only gas safe board. Working with gas appliances is dangerous, and employing an illegal gas fitter could see you joining the whopping 52% of Bristol homes that are already in danger from poor and unsafe gas work.

If you’re unsure on how to check whether or not a tradesperson is on the gas safe register, read our guide here:

Low Boiler Pressure

When your boiler pressure drops, you central heating system can malfunction in a multitude of ways. The key to checking if your boiler’s pressure level is too low, is to look at it’s pressure gauge. If the gauge is measuring below 1, then the pressure is too low.

The pressure might be faltering for a number of reasons; recently bled radiators, a water leak or the pressure valve might need replacing. The first, and easiest thing to check for is a visible leak in the system as if you’ve got enough technical know how you can fix this yourself. If you’re comfortable enough doing so, you should try to repressurise the system in accordance with the manual, if not, call out a plumber to properly assess your boiler.

Your Boiler is Dripping or Leaking

A leaking boiler is an easy thing to spot, but a far more difficult thing to assess and fix. The reason your boiler is leaking can be determined from where the leak has sprung, but you should always call out a Gas Safe Registered engineer to determine the cause and patch up the leak.

The most likely reason your boiler is leaking is that an internal component has broken, commonly a pressure valve or pump seal. If your pressure valve is causing the leak, it may be a sign that your boiler pressure is too high; or if it is the pump seal, it could be because the seal has worn from use and needs replacing. Either way, an engineer should have no trouble fixing these issues.

Alternatively, you might find that it is the pipes or tank of your boiler that are leaking, resulting from long-term corrosion or an incorrect system fit. If left to develop long enough, these issues may require you to totally replace your boiler.

If you, unfortunately, do need to replace your boiler, please read our Ultimate Boiler Guide to ensure you get the best boiler for your home.

You Can Hear Strange Noises Coming from Your Boiler

If you’re hearing strange banging or gurgling noises your house isn’t haunted, it’s probably just air trapped in your pipes, low water pressure or – if you’re hearing whistling noises – kettling. Alternatively, in older systems, it could be a symptom of a slightly more urgent issue such as imminent pump failure.

You may be able to figure out the issue with your boiler dependent on the noise it is making, particularly with kettling, which we’ll discuss below, but it is probably safer to get a plumbing engineer out.

The Pilot Light Has Gone Out

If the pilot light on your boiler has gone out, the cause could be anything from a simple draught, a deposit or a broken thermocouple.

You can reignite a pilot light yourself. But before you do, always check there are no underlying issues with your gas supply. If you’re not receiving any gas, but your stopcock is on, or if your other gas appliances aren’t working, you should contact your gas supplier for a status update.

If that isn’t working, or if there is a different issue, call out an expert. Whilst non-intrusive and simple fixes like reignition of a pilot light are okay for you to complete with the guidance of a manual, it is safer to leave any more technical work to a certified engineer.

Your Condensate Pipe Has Frozen

In condensing boilers, there is always a condensate pipe which transports the acidic water, a product of the waste gas, out of the boiler. Usually, this pipe transports the water to a drain outside, which means that due to its location, it is at a significant risk of freezing over during the colder months.

Whilst the risk of freezing can be mitigated through the regular use of your boiler and protective insular padding, there is still a small possibility that it can happen. Although many boilers now display a fault code or notify you if your pipe has frozen, it is always worth regularly checking on the pipe – usually, a white plastic pipe located underneath the boiler – to ensure it’s not at a risk of freezing or bursting.

If you suspect that your condensate pipe has frozen, you can pour on warm water, or use warm compresses, to slowly thaw out the frozen water inside. However, if you feel unqualified or unsure, don’t hesitate to call out an emergency plumber.

Boiler Thermostat Problems

If your thermostat is switching the heating on and off at random or is just losing accuracy, unfortunately, there’s not much you can do in the way of intermediary fixes and the best course of action is to buy a replacement.

However, before you do so, ensure that it’s not an easily rectifiable problem that you’ve overlooked, such as incorrect scheduling settings. Alternatively, your home might be already at the maximum heat limit set for your boiler, meaning your thermostat won’t allow your boiler to heat your home any higher. If this is the case, readjust your settings and increase your temperature in small increments until you find a level that you’re comfortable with.

If it is none of the above, then it’s likely your thermostat has just become old and needs replacing.


Doing what it says on the tin, kettling is the colloquial name for a buildup of sludge or limescale on your boiler’s heat exchanger, which causes the weird rumbling or whistling noises similar to an old-school kettle reaching boiling point. The aural annoyance comes from the build up of these deposits restricting the water flow within the heat exchanger, causing the water to steam, boil and whistle.

Outside of the strange sounds, kettling can cause long-term damage to both your boiler and finances. Not only does it force your boiler to work harder under the extra strain, but, in turn, it makes it much more expensive to run and can shorten the lifespan of your boiler considerably.

A plumber will be able to safely flush out the deposits without damaging the rest of the system, ensuring that it is back to working order.

Your Radiators Aren’t Getting Hot

If you find that only certain radiators in your home are heating up, or if only the bottom section of your radiators are heating up, it’s most likely down to a buildup of air or sludge in your system, causing an unequal distribution of heat.

If it is a buildup of air, which you can only really diagnose though trial and error, there are two courses of action you can take:

  • If only the bottom of the radiator is warming up, you can bleed your radiator, which is fairly straightforward with a cursory google search.
  • If certain radiators aren’t getting hot, you can try to balance them by adjusting the valves of every radiator within your property, making sure they’re each receiving enough hot water to work correctly. This can also be done without the help of a plumber providing you are confident enough to try.

If you perform either of the above treatments and your radiators still are not working, then it is most likely that a sludge is impacting the flow of water to your radiators. To correct this, you will need to call out a plumbing engineer to chemically clean or flush out your system.

Your Boiler Keeps Switching Itself Off

If your boiler is switching off without any instruction, it could be a result of a number of issues that we’ve discussed above, such as a problem with the thermostat or air, or a closed valve, blocking the flow of water.

It’s best to call out a registered plumbing engineer to assess your boiler, as boiler failure can result from any one of a number of causes.

If you’re having trouble with your boiler and would like more advice on the topic, please don’t hesitate to contact us on 01179 093 967 to speak to one of our plumbing experts.

All of our engineers are Gas Safe Registered and available to help out with any issue, no matter how big or small.