Every winter a good share of the boiler call-outs we attend in Glasgow and Lanarkshire turn out to be something the homeowner could have fixed in five minutes — a pressure top-up, a frozen pipe, a timer that's lost its settings after a power cut. We'd rather you kept the £85 and had the heating back on tonight.
Work down this list in order. If you get to the end and it's still not working, book a repair and tell us what you've already tried — it helps the engineer arrive with the right part.
Stop and read this first. If you smell gas, if the boiler's flame is yellow or orange instead of blue, if there's black soot around the boiler or a pilot light keeps going out, or if anyone in the house has headaches, dizziness or nausea that clears when they go outside — switch the boiler off, open windows, get everyone outside and call the National Gas Emergency Service on 0800 111 999. Don't try anything below. Gas work is for Gas Safe registered engineers only; never open the boiler casing yourself.
1. Is it actually the boiler?
Check the obvious things everyone skips:
- Power. Is the boiler display lit? Check the fused spur switch next to the boiler and the fuse or breaker in the consumer unit. A tripped RCD after a storm is a common culprit.
- Gas. Does the hob light? If not, the problem is your gas supply, not the boiler. Check the meter isn't showing an error and that a prepayment meter has credit.
- Other appliances. If the gas fire and hob work but the boiler doesn't, carry on down the list.
2. Check the pressure gauge
Look for a dial or digital reading on the front of the boiler. When the system is cold it should sit between 1 and 1.5 bar (green zone on most gauges).
- Below 0.5–1 bar: the boiler will lock out with a low-pressure fault (Worcester EA or 224, Vaillant F22 or F75, Ideal F1, Baxi E119, and so on). Re-pressurise using the filling loop — usually a silver braided hose with one or two small valves under the boiler. Open the valve(s) slowly until the gauge reads about 1.2 bar, close them, then reset the boiler. Your manual or the manufacturer's website has a video for your model.
- If it drops again within days, you have a leak somewhere or a failing expansion vessel. That needs an engineer.
- Above 2.5–3 bar: don't ignore it. Bleed a radiator to release some water. If the pressure keeps rising when the heating runs, the expansion vessel probably needs recharging — see our repair price guide.
3. The frozen condensate pipe — Scotland's favourite fault
If it's below freezing outside and your boiler has stopped with a gurgling noise or a fault code, this is the first thing to suspect. Modern condensing boilers produce water that drains through a plastic pipe, usually about 22mm or 32mm wide, running outside to a drain. When that pipe freezes, the boiler shuts down to protect itself.
The fix:
- Find where the pipe exits the wall and follow it to the drain. The frozen section is usually at the open end or a bend.
- Pour warm (not boiling) water over the pipe, or hold a hot water bottle or a microwaveable heat pack against it. Never use boiling water — it can crack the pipe.
- Once thawed, reset the boiler.
To stop it happening again, an engineer can insulate the pipe, increase its diameter, shorten the external run or re-route it internally. Ask about this at your next service — it's cheap and it saves a January call-out.
4. Reset the boiler
Most modern boilers have a reset button or a reset option in the menu. Hold it for a few seconds and wait. Lockouts after a power cut, a pressure blip or a brief gas interruption often clear with a single reset. If it locks out again straight away, or you're resetting it every day, stop. Repeated resets can mask a real fault, and the code it shows is exactly what the engineer needs to know — take a photo of it.
5. Check the timer and thermostat
After a power cut or the clocks changing, timers can lose their programme.
- Is the programmer set to "on" or "timed", and is the current time correct?
- Is the room thermostat turned up above the room temperature? Try 25°C for a test.
- If you have a smart thermostat (Hive, Nest, Tado), is it connected? Batteries in wireless thermostats and receivers are a regular cause of "no heating" calls.
- Are the thermostatic radiator valves (TRVs) turned up? A radiator with its TRV at zero will never heat, boiler or no boiler.
6. Heating but no hot water (or the reverse)
If you get one but not the other on a combi boiler, that usually points to the diverter valve, the component that switches between heating and hot water. It's an engineer job, but knowing this saves diagnosis time. On a system boiler with a hot water cylinder, check the cylinder thermostat and the motorised valve on the pipework (you may hear it click or find it stuck).
7. Radiators cold at the top, warm at the bottom
That's air. Bleed the radiator with a radiator key until water appears, then re-check the boiler pressure (bleeding lowers it — see step 2). Radiators cold at the bottom but warm at the top are sludge, which is a different job and usually needs a power flush or a magnetic filter clean.
When to call us
Book an £85 fixed call-out if:
- The boiler locks out repeatedly or shows a fault code that isn't low pressure
- Pressure keeps dropping and you can't find a leak
- You have heating but no hot water, or vice versa
- The boiler is making banging, whistling or kettling noises
- There's water leaking from the boiler or the pressure relief pipe outside
- The pilot light or burner won't stay lit
Describe the fault and, ideally, upload a photo of the display when you book. Your confirmation email has a live tracking link so you'll know exactly when the engineer is on the way. If it turns out the repair isn't worth doing, we'll tell you — fixed-price replacement boilers start from £2,500 and you can get a price online.
Frequently asked questions
Why has my boiler stopped working in the cold?
Nine times out of ten in Scotland it's a frozen condensate pipe. Thaw it with warm water and reset the boiler.
What pressure should my boiler be?
Around 1 to 1.5 bar when cold. It will rise a little when the heating is on.
How many times can I reset my boiler?
Once or twice is fine. If it keeps locking out, book an engineer — repeated resets can hide a fault.
Is it safe to top up boiler pressure myself?
Yes, using the filling loop as described in your boiler manual. Don't open the boiler casing — that's for Gas Safe registered engineers only.
My boiler is working but the radiators are cold. Why?
Check the thermostat, TRVs and timer first, then bleed the radiators. If they're cold at the bottom, it's sludge and worth a conversation about a power flush.
Written by Stephen, Lead Engineer at Titan Heat. Titan Heat is a Gas Safe registered heating and plumbing business (Reg. No. 982732) serving Glasgow and Lanarkshire.
