Boiler broken down in winter? What to do right now

A boiler breakdown in winter is one of the most stressful things that can happen in a home. Here's what to do — starting in the next five minutes.

First: is this a gas emergency?

Before anything else — if you smell gas, suspect a carbon monoxide leak, or see any signs of immediate danger, stop reading this and act on gas emergency guidance immediately. Call the Gas Emergency Service on 0800 111 999 (free, 24 hours). Don't use light switches, phones, or anything electrical in the property until you're outside. Open windows and doors if it's safe to do so.

If the situation is a boiler fault — no heat, no hot water, an error code showing, or the boiler just not firing — read on.

Step 1: Check the basics before calling anyone

Many boiler callouts are resolved without an engineer visit. Work through these first:

Check the pressure gauge. Most combi and system boilers have a pressure gauge on the front. The needle should sit between 1 and 2 bar when the system is cold. If it's below 1, or reads zero, low pressure is likely the cause of the lockout. Your boiler manual will show you how to repressurise — it typically involves a filling loop beneath the boiler.

Check for an error code. Modern boilers display fault codes when they lock out. Google your boiler brand plus the error code — e.g. "Worcester Bosch E9" or "Ideal F1" — and you'll often find the specific fault described. Codes like F1 (low pressure), F22 (no water), or E9 (overheat) are often straightforward to understand, even if the repair isn't DIY.

Try a single careful reset. Most boilers have a reset button — a small button or dial marked with a symbol similar to a refresh arrow. If your manual permits it and there's no obvious gas smell or safety concern, one reset attempt is reasonable. If the boiler fires and then locks out again within the hour, stop resetting — you're masking a fault that needs diagnosis.

Check if it's only heating or only hot water. A combi boiler that produces hot water but no heating, or heating but no hot water, has different likely causes. Note which is failing and report it when you book.

Check your thermostat and timer. It sounds obvious, but check the room thermostat is set above the current room temperature, and that the programmer hasn't been accidentally switched to off or summer mode. A flat thermostat battery can also silently kill the heating.

Step 2: Keep the property from getting dangerously cold

While you wait for an engineer:

• Close internal doors and focus heating on one or two rooms if you have any supplementary heating (oil heaters, fan heaters).
• Protect vulnerable pipes — if overnight temperatures are forecast below zero, know where your stopcock is in case a pipe freezes and bursts.
• Hot water workarounds — an electric shower, a kettle, or a portable camping shower can all bridge the gap for a few days.
• Vulnerable occupants — if the property has elderly residents, young children, or anyone with a health condition that makes cold temperatures dangerous, flag this explicitly when you book. It prioritises the callout.

Step 3: Book the repair

When you call or book online, have the following ready:

• Boiler make, model, and approximate age (usually on the front panel)
• The error code or fault description — what you see on the display
• Whether it's heating, hot water, or both that's failed
• Whether a reset helped temporarily or not at all
• Any sounds — banging, hissing, clicking that doesn't resolve into a flame
• Whether there are vulnerable occupants in the property

This detail allows an engineer to prepare and arrive with likely parts — reducing the chance of a second visit.

When to book HeatNI

If you're in Belfast, Bangor, Lisburn, Newtownards, Holywood, Dundonald, Comber, or Donaghadee and your heating or hot water has failed — book a callback. We prioritise genuine winter emergencies, and we'll be honest about timing and next steps when we call back.

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For confirmed gas escapes or carbon monoxide emergencies: call 0800 111 999. This guide is for boiler faults, not gas safety emergencies.