Common Boiler Problems and How to Fix (Some) of Them

There’s nothing more inconvenient in the world than having a boiler problem at home. No matter the time of year, the simple fact is we all need hot water in our homes. But what are some of the most common boiler problems, and how can you fix some of them?

We specifically say that only some of these common boiler problems can be solved by DIY, as legally, in the UK, you need a registered Gas Safe engineer to work on any gas appliance in your home.

It’s also important to exercise caution when hiring a professional*. Unfortunately, some individuals may falsely claim to be certified. Always verify their credentials on the Gas Safe Register website before allowing them to work on your boiler.

Now, let’s talk through some of the most common boiler problems.

Let’s start with the common boiler problems and how to fix them if you’re legally allowed.

Common Boiler Problems

Again, if you’re uncertain about your diagnosis, call a professional*. While not having access to hot water is inconvenient, compounding the problem can be incredibly dangerous.

Let’s talk about arguably the most common issue related to boilers.

Leaking boiler

A typical boiler problem is that your system is leaking. The reasons for a leaking boiler will vary widely.

A leaking boiler can be caused by:

• Pressure issues
• Loose joints
• And damaged seals or body

Pressure Issues

Fluctuating water pressure is the most likely culprit for a leaking boiler. All boilers have an outlet pipe to release this pressure. This pipe is not pressurised and is assembled without any sealed fittings.

If there is a gradual drip from the outlet pipe, it is nothing to worry about. However, if there is a large amount of water pouring out of the outlet pipe, the pressure in the system is too high.

You can check this on your boiler’s gauge. Generally, if the gauge indicates the pressure is in red, it’s too high, and in green, it’s okay.

Call a Gas Safe engineer to bleed your boiler and lower the pressure to correct the system.

Loose Joints

All materials exposed to hot and cold conditions expand and contract. Over time, this expansion and contraction will loosen joints and fittings. When installing a new boiler, your qualified engineer will tighten the joints.

A sure sign that you have loose joints is water leaking from it. To get a better idea of the source of the leak, you can use a dry cloth to dab the area and wait for water to reappear.

If you are sure that your leak is coming from a joint, a simple quarter turn with a spanner might fix the issue. However, if you can’t locate the leak or your efforts are unsuccessful, call a professional* to complete the job.

Damage to Seals and Body

As mentioned, your boiler will expand and contract over time. This can loosen joints and cause seals to crack.

Over time, the rubber seals in your system will harden and break apart, resulting in leaks from the faucet areas.

If you notice a faucet leaking, call a professional* to replace the seal.

If you live in an old home, your boiler’s body could have cracked. If so, turn off the water and gas and call a professional* to replace it.

Low Boiler Pressure

Your home’s boiler system relies on maintaining the correct water pressure to work correctly. Some boilers will stop working if the pressure in the system drops too low. When a boiler stops working due to low pressure, it will display an error message.

Each brand will have its own unique code.

Another indicator is the boiler’s pressure gauge.

A low-pressure error is usually caused by a leak in the system. If there’s no leak, as a homeowner, you can try to re-pressurize the system by following the instructions in the manufacturer’s manual.

If a leak within the boiler is causing the low pressure, call a professional* to fix the problem.

Frozen Condensate Pipes

When the seasons change and the colder months slip in, your boiler needs to be working at 100%. Your boiler’s condensate pipe removes all the acidic waste from the boiler itself and allows it to drain away outside into the stormwater system.

During the colder months, this pipe can freeze, blocking the waste from draining away. Usually, this issue will display an error code on your boiler.

Another sign that your boiler’s condensate pipes are frozen is that your home’s system starts making an unusual noise when it is fired up. The noise can be described as a gurgling sound coming from the boiler or the pipes circulating heated water around your home.

This common boiler problem is simple enough to solve as a DIY project. Fill a jug with warm water from the kitchen kettle and slowly pour it over the pipe. Repeat this process until you’re confident that the condensate pipe is unfrozen.

To prevent your condensate pipes from freezing again, wrap them in insulation. However, if a pipe freezes outside, you can have an engineer relocate it to where this is less likely to happen.

It’s also worth noting that your boiler will display an error message if the condensate pipes have frozen.

These codes are:

A Noisy or Kettling Boiler (whistling)

While it is normal for your boiler to produce a low hum, it’s a bit unusual for it to:

• Gurgle
• Whistle
• Knock/Tap
• Or to start banging

The sudden introduction of a new noise from your boiler is never a good sign. If your boiler produces a sound similar to a kettle boiling, this is usually a sign of a limescale build-up or deposit in your system.

Limescale isn’t usually an issue unless you’ve skipped your annual service. During an annual service, a gas engineer will ensure that the system is cleaned with a limescale remover.

If your boiler gurgles when running, it is usually caused by trapped air in the system. This gurgling will also be accompanied by a cold spot at the bottom of your home’s radiators.

You can fix this issue by bleeding the radiators yourself. If this doesn’t work, the most likely problem is a sludge build-up. Sludge in your radiator is usually made up of rust residue and other compounds that have developed over time and use. To clear out sludge from your system, you will need help from a professional*.

When your boiler makes a knocking or tapping noise, the most likely cause is something trapped in the flue. To test if this is the cause of the noise, you will need to perform a simple test, which will require you to hold your hand over the vent.

If you can feel an airflow, this will indicate that there’s no blockage. But if not, you must call a professional* to clean the flue.

The final noise is an abnormally loud humming coming from the boiler. This problem could be a few issues, which include:

• Water pressure being too high
• Your boiler’s pump is running too fast
• Or there’s a loose component

Only the pressure problem can be solved via DIY, whereas the others will require a Gas Safe engineer.

Whenever there is a strange sound, address it as soon as possible.

Pilot Light Keeps Going Out

If you own an older boiler, it is common for the pilot light to go out. The main reason is that older models do not have an electronic ignition, so they must be kept on to light the fuel in the combustion chamber.

For those stuck with an ongoing pilot problem in an older boiler, you can call a gas engineer to fix it. But it might also be time to buy a new boiler.

Another reason a pilot light will go out frequently is a simple draught blowing out the flame. In this situation, blocking the source of this draft will solve the problem.

If you’re sure it is not the wind or the age of your boiler, you can be semi-certain it is a faulty thermocouple switching off the gas supply. But generally, any issue with a pilot light is related to gas supply, so call the professional*.

If you can smell gas, turn off the supply and call in a Gas Safe engineer.

Central Heating Works, But No Hot Water From The Boiler?

You’d be within your right to be confused, but this can happen if your boiler is part of a more extensive system. The most likely cause of this issue could be one of the following:

• The system’s program
• Hot water cylinder thermostat
• Or a faulty radiator valve in your system

Simply put, there’s a part that does not open and close when the correct temperature is reached.

For those with a wireless thermostat, the problem could simply be an issue with the devices’ communication. Resetting the system will often solve the problem.

Or if the battery in the thermostat that regulates your gas boiler’s temperature has run out, it could be a simple battery replacement.

But if the battery does need replacing, it could also be related to the boiler not turning on.

If there is no hot water from the taps or in certain radiators throughout the home, it is most likely an issue with the valve.

However, in the situation where the heating is not working, and the water from the taps is hot, the likely culprit is either:

• Accidentally switching off the heating
• Broken boiler component
• Or a faulty diverter valve

A faulty diverter valve is the most likely cause of the problem.

Boiler Is Not Heating Water High Enough

As you can now imagine, if your boiler is not heating your water high enough, there could be a few reasons for this, which include:

• Faulty boiler components
• Air in the system
• Faulty thermostat
• Low pressure
• Faulty heat exchanger
• Leaking boiler and system
• Faulty diverter valve
• And more

Your boiler works within a system of balances. If any part of this system isn’t correctly calibrated, the boiler will not heat the water enough.

Checks To Perform Before Calling The Professionals

Finding out what the exact problem is with your boiler is complicated. This is also why most of the UK population, those who are not Gas Safe engineers, are not allowed to tamper with their boilers.

So, if you’re now reluctantly considering calling in the Gas Safe engineer, you can perform a few quick checks to ensure they are needed. These include:

• Ensure the gas supply operates as it should, and test other appliances to see if they work.
• Check the power supply. Sometimes, it can be a simple tripped fuse.
• Look at your heating control and read the manual about resetting the thermostat.
• Take a look at your boiler’s pressure. We’ve described what to do when the pressure is too low or high.
• And finally, hit the reset button.

If these last checks haven’t worked, it’s time to call *a professional.

*When we say “call a professional,” we mean contact us to help you, and we’ll be at your home within 48 hours.