Common Boiler Problems: Simple Fixes to Try and When to Call an Engineer

Are you experiencing issues with your boiler? Most common boiler problems, from low pressure to cold radiators or no hot water, have a simple cause that you can often check safely yourself. That said, anything involving the gas supply or the inside of the boiler should always be left to a Gas Safe registered engineer.

This guide works through the most likely faults in the order an engineer would check them, starting with the quickest and simplest, so you can rule things out calmly and know exactly when it is time to pick up the phone.

Boiler Not Working? Start With These Basic Checks

Finding your boiler not working on a cold morning is frustrating, but a surprising number of callouts turn out to have a simple cause. Good boiler troubleshooting always starts with the basics. First, check the boiler has power: is the display lit, and has a fuse or switch tripped?

Next, look at your thermostat and timer, because a change to the clocks or a flat thermostat battery can stop the heating from coming on. It is worth checking whether your gas hob works, which tells you the gas supply is fine, and whether a prepayment meter needs topping up. If none of these explains the problem, you can press the reset button once. If the boiler still refuses to fire up, the pressure gauge is the next place to look.

How to Fix Low Boiler Pressure

Low pressure is one of the most common boiler problems, and most modern boilers will shut down to protect themselves when it drops too far. Your pressure gauge should read between 1 and 1.5 bar when the heating is off (check your manual).

If you are wondering how to fix low boiler pressure, the answer on most combi boilers is the filling loop, a small flexible hose or key underneath the boiler that lets water in from the mains. Open the valves slowly, watch the gauge rise to the correct level, then close them. If the pressure keeps dropping, you may have a leak that needs an engineer. It also dips slightly after bleeding, so knowing how to bleed a radiator goes hand in hand with keeping your pressure right.

Cold Radiators and How to Bleed a Radiator

Radiators that are warm at the bottom but cold at the top usually have trapped air, while those cold at the bottom are often clogged with sludge. Trapped air can be dealt with easily by simply bleeding the radiator. It takes minutes – here’s how:

• Turn off the heating and let the radiators cool
• Fit a radiator key to the top bleed valve
• Hold a cloth below and turn the key anticlockwise
• Close the valve once water appears

Afterwards, check your gauge, and if it has dropped, follow the steps on how to fix low boiler pressure above. Sludge, on the other hand, is a problem that’s a little more difficult to resolve, as it needs a power flush, a professional clean that pushes water through your system at high flow.

If you find that your heating is not working at all, the boiler itself is the next place to look.

No Heating or No Hot Water? Common Causes Explained

Inside the boiler, a handful of faults account for most cases of lost heating or hot water. In winter, the most likely culprit in homes is a frozen condensate pipe, the plastic pipe that carries wastewater from a condensing boiler to a drain outside. When temperatures drop below freezing, this pipe can ice over and the boiler shuts down, often showing a fault code.

You can usually thaw it by pouring warm (never boiling) water over the outside section, then resetting the boiler. If you have heating but no hot water, or the reverse, a faulty diverter valve, which directs hot water to your taps or radiators, may be to blame. Your boiler will often tell you what’s wrong in the form of an error code. Knowing what these codes mean is, therefore, worthwhile.

Understanding Boiler Error Codes and Strange Noises

Boiler error codes vary between manufacturers, so the same code can mean different things on different makes, and our website, your manual, or the manufacturer’s website is the best place to check. Some point to issues covered here, such as low pressure or a frozen condensate pipe, while others signal a component fault that needs an engineer.

Noises help too. Banging or rumbling often suggests limescale or sludge, gurgling tends to mean trapped air, and whistling can point to a pump or pressure issue. Many common boiler problems can be handled with a simple check, but if your heating is not working and the same code returns after every reset, the DIY stage is over.

When to Call a Gas Safe Engineer (and How M J Burt Property Maintenance Can Help)

Knowing when to call a Gas Safe engineer matters most where safety is concerned. Call one if you notice any of these:

• A smell of gas
• Your carbon monoxide alarm sounding
• Sooty staining around the boiler or a yellow flame
• Water leaking from the boiler or pipework
• The same fault returning after repeated resets

If you smell gas or your carbon monoxide alarm sounds, open windows, turn off the gas at the meter, leave the property and call the National Gas Emergency Service on 0800 111 999. Working on gas appliances without Gas Safe registration is illegal. At M J Burt Property Maintenance, our Gas Safe registered engineers have handled common boiler problems across Poole and Bournemouth since 1988, so whether it is a boiler not working or a replacement, we can help.

Keep Small Boiler Faults from Becoming Big Ones

Most boiler faults start small. Checking the power and controls, topping up the pressure, bleeding radiators and thawing a frozen condensate pipe will solve many of them, while error codes, strange noises and safety warning signs tell you when to call in a professional.

An annual boiler service is the simplest way to stop common boiler problems before they start. Call our team on 01202 721955 or use our contact form to book your service or arrange a repair.