8 Common Boiler Problems (And What to Do About Them)

By The Bord Gáis Energy Team - Published 21 May 2026

A boiler breakdown rarely picks its moment. It's usually a Tuesday in January, definitely one of the colder months, the heating's gone cold, and you've no idea where to start. The good news? Not every boiler issue needs a call-out. Some of the most common problems have simple fixes you can try yourself, safely, and without any specialist knowledge.

Here are nine issues Irish homeowners run into most, what's causing them, and what to do.

In this article:

• Why boiler issues are common in Ireland
• Low boiler pressure
• Frozen condensate pipe
• Incorrect boiler or thermostat settings
• Pilot light has gone out
• Boiler lockout and reset issues
• Radiators not heating properly
• No hot water but heating works
• Strange boiler noises
• When to call a professional
• Keep your boiler running efficiently with Bord Gáis Energy
• FAQs about gas boilers in Ireland

Why boiler issues are common in Ireland

Ireland’s climate plays a big role in gas boiler performance. Cold snaps, damp conditions and fluctuating temperatures can put pressure on heating systems. Combine that with everyday wear and tear, and it’s easy to see why problems arise.

Staying proactive is key. If you haven’t already, it’s worth reviewing these essential maintenance tips in our guide to boiler care.

1. Low boiler pressure

What you'll notice:

• The boiler keeps switching off
• Radiators aren't heating evenly. Especially upstairs
• Banging or gurgling from the pipes

What’s happening:

Low pressure prevents your boiler from circulating water effectively around your heating system.

What to do:

Check the pressure gauge. If it's sitting below 1 bar, use the filling loop to bring it back up to between 1 and 1.5 bar. You may need reset after.

If pressure keeps dropping back down, that usually points to a leak or a faulty component and it's time to bring in an engineer.

2. Frozen condensate pipe

What you'll notice:

• The boiler won't fire up
• Gurgling or bubbling sounds
• It's happening during a cold spell.

What’s happening:

Condensing boilers produce wastewater that drains through an external pipe. When temperatures drop, that pipe can freeze solid.

What to do:

Carefully pour warm water over the pipe to thaw it. Not boiling, just warm. A hot water bottle works well too. Once the blockage clears, reset the boiler. This is one of the most common winter callouts in Ireland. If it keeps happening, insulating the pipe is worth considering.

You can also read more about protecting your pipes.

3. Incorrect boiler or thermostat settings

What you'll notice:

• Heating not coming on at expected times
• Boiler not responding or working properly
• Blank or unresponsive thermostat screen

What’s happening:

Power cuts, the clocks changing, or an accidental button press can all throw off your settings.

What to do:

Check your timer and thermostat. Make sure the temperature is set to around 20–21°C. Replace the batteries in your thermostat if needed, and confirm the heating is switched on at the boiler itself.

4. Pilot light has gone out

What you'll notice:

• No visible flame
• Boiler not igniting

What’s happening:

Older boilers use a pilot light to ignite the gas. Your pilot light can go out due to drafts or internal faults.

Simple fix:

Follow your boiler manual to safely relight the pilot light.

⚠️ One important note: If you smell gas, see soot around the boiler, or notice a yellow or flickering flame, just stop. Don't attempt any fixes. Turn off the appliance and call a registered gas engineer straight away.

5. Boiler lockout and reset issues

What you'll notice:

• Error codes on display
• The boiler keeps shutting itself down
• Red warning or lockout light

What’s happening:

Your boiler is designed to lock out when it detects a fault. It's a safety feature, not a malfunction. It's telling you something needs attention.

What to do:

If your boiler has a reset button, try pressing it. If the issue persists, it may be linked to low pressure, blocked components, or internal faults that are preventing your heating from working properly that require professional attention. If pressing the reset button does not fix the problem it might be best to book a service.

6. Radiators not heating properly (air or sludge build-up)

What you'll notice: 

• Cold spots on radiators
• Radiators warm at the bottom but cold at the top
• Slow heat-up times

What’s happening:

Air trapped in the heating system or sludge build-up in or near your radiators can prevent hot water from circulating properly.

What to do:

Bleed your radiators using a radiator key to release trapped air. If the issue continues, your system may need a power flush to remove sludge. It's a straightforward job, but a power flush is best left to a professional.

7. No hot water but heating works

What you'll notice:

• Radiators heating normally
• No hot water from taps

What’s happening:

This is often linked to a faulty diverter valve, which controls whether heat goes to your radiators or hot water system.

What to do:

Check your boiler settings first to ensure hot water is enabled. If the issue persists, a qualified engineer will need to inspect or replace the valve.

8. Strange noises (kettling, banging or whistling)

What you'll notice:

• Whistling or kettling sounds
• Loud banging when heating starts
• Unusual vibration noises

What’s happening:

Limescale or sludge build-up is restricting water flow, which causes localised overheating and pressure changes in the system.

What to do:

Check your pressure and bleed the radiators. Beyond that, there's no safe DIY fix. Persistent noise usually means the system needs cleaning or a component replaced by an engineer.

When to call a professional

While some boiler issues are safe to troubleshoot, others require expert attention. You should always contact a qualified gas boiler engineer if:

• You smell gas
• Your boiler repeatedly fails or resets
• There are visible leaks or damage
• The flame is yellow or unstable

Regular boiler servicing from a Registered Gas Installer (RGI) engineer helps prevent many of these issues before they escalate.

Keep your boiler running efficiently with Bord Gáis Energy

Many boiler problems can be avoided with regular checks and servicing. Small actions like monitoring pressure, checking for unusual noises, and ensuring a clean blue flame can make a big difference to the performance and safety of your boiler and gas supply.

If your boiler isn’t working as it should, or you’d rather have peace of mind, you can arrange a professional service or boiler repair today.

We can also handle new boiler replacement installations if your current one is rendered unsafe or past its lifespan.

A well-maintained boiler doesn’t just keep your home warm. It helps you stay in control of your energy use, reduce costs, and avoid unexpected breakdowns when you need heat the most.

FAQs about gas boilers in Ireland

How often should I service my boiler?

Once a year. Annual servicing helps maintain efficiency, reduce breakdown risk and extend the life of your boiler.

What pressure should my boiler be?

Typically between 1 and 1.5 bar when the system is cold. But always check your manufacturer’s guidance and if in doubt contact an engineer.

Why does my boiler keep losing pressure?

This could be due to a leak, a faulty pressure relief valve or worn components. It should be checked by an engineer.

Is it safe to fix boiler problems myself?

Only minor issues like pressure adjustments or resetting the system are safe. Anything involving gas or internal components should only be handled by a professional.

Why is my boiler making loud noises?

This is often caused by trapped air, limescale, or sludge. It usually requires professional cleaning or maintenance.