Every year it happens the same way. The weather turns genuinely cold over a weekend in late October, and by Monday morning our team are taking calls from one end of the city to the other. Boilers that worked fine in March won’t fire, radiators come on stone cold, and more pressure gauges than you’d think sit flat on zero.
None of those systems broke on that Monday. They’d been quietly faulty since about April, and nobody noticed, because nobody had the heating on since spring.
The difference between a 20-minute fix in September and a 3-day wait in November usually comes down to when you found out.
Here’s what’s worth doing now, in the order we’d do it ourselves.
1. Turn It On Before You Need It
We always advise running the heating for half an hour on a mild day. That’s the whole test, and it’s the one thing most people skip.
You’re listening and looking for four things.
- Does the boiler fire up the first time, or does it lock out?
- Do all the radiators get warm, or are some cold?
- Are there noises that weren’t there before, a banging or a kettling sound?
- Do you smell gas, or do you see any water under the boiler?
If everything passes, brilliant, you’re done in half an hour. If something fails, you’ve found it in September when engineers have availability, rather than in the middle of a cold snap when everyone in Cardiff is ringing at once.
2. Bleed The Radiators
Air collects at the top of radiators over the summer while the system sits idle. That air stops hot water from reaching the top of the panel, so the radiator heats at the bottom and stays cold at the top, and the room never really warms up.
It’s a genuinely simple job with a bleed key and a cloth, and we’ve written a full guide on how to bleed a radiator if you’ve not done it before. As a reminder, try to work from upstairs to downstairs, and keep an eye on your boiler pressure afterwards because bleeding drops it.
3. Check The Boiler Pressure
Most systems want roughly 1 to 1.5 bar when the heating is cold, but if the needle is near zero, the system needs topping up before it’ll run properly, and many boilers simply won’t fire below a certain point.
Topping up once is normal, particularly after bleeding. However, topping up every few weeks isn’t, and it means water is escaping somewhere. That’s worth reading our guide on combi boiler pressure for, and getting it looked at rather than living with it.
4. Feel Each Radiator Top & Bottom
This is the check that tells you the most and takes the least time. With the heating running, put a hand on the top of each radiator, then the bottom.
Cold at the top usually means air, and bleeding sorts it. Cold at the bottom is a different problem entirely. That’s sludge, the black iron oxide that builds up in heating systems over years, settling in the bottom of the panel and blocking circulation. Bleeding won’t touch it.
One sludged radiator can sometimes be isolated and flushed on its own. A system where several are cold at the bottom usually needs a power flush, though not always, and we’d want to look before recommending one. If a radiator is cold all over rather than in one half, our guide on radiators not heating up covers the usual causes.
5. Lag The Condensate Pipe
If we had to pick one job on this list that prevents the most winter callouts, it’s this one.
Modern condensing boilers produce waste water, which drains away through a plastic condensate pipe. In many Cardiff properties, that pipe runs outside, up an external wall, or along the back of the house. When the temperature drops below freezing overnight, the water sitting in it turns to ice, the pipe blocks, and the boiler shuts itself down as a safety measure.
The boiler isn’t broken. It’s doing exactly what it’s designed to do. But you’ve got no heating on the coldest morning of the year, and so has half the street, which is why those days are the busiest we get.
Lagging the external section with proper pipe insulation costs very little and takes minutes. If yours has frozen before, it’ll freeze again, so it’s worth either insulating it properly or altering the run.
6. Test The Thermostat & Programmer
Wireless thermostats run on batteries, and batteries die quietly. A thermostat with flat batteries doesn’t tell the boiler to fire, and the boiler gets blamed for a fault it doesn’t have. We’ve been called out to more than one dead heating system that needed two AAs.
While you’re there, reset the programmer. The clocks change at the end of October, and plenty of older programmers won’t adjust themselves, so your heating ends up coming on an hour out for the rest of winter.
7. Open The Radiator Valves You Closed in Summer
A lot of people turn radiators down or off in rooms they weren’t using over the summer. Thermostatic valves that have sat closed for months often seize in that position, and the pin underneath sticks.
Turn every valve fully open now. If one won’t budge, take the plastic head off and press the metal pin underneath with your thumb. It should move freely and spring back. If it’s stuck solid, the valve head needs replacing, which is a small job now and an annoying one in December.
8. Book The Service Before Everyone Else Does
An annual boiler service is the one thing on this list you can’t do yourself, and it’s the one that catches the faults the other seven checks won’t show. It’s also usually a condition of keeping your manufacturer’s warranty valid.
September and early October are the right time to book. By November, the diary is full of emergency plumbing callouts, and a routine service competes with people who have no heating at all.
One Last Thing Worth Knowing
Most of what’s on this list takes an afternoon and costs almost nothing. It buys you the chance to find out about problems in September rather than on the coldest night of the year.
Something not working as it should? Get in touch, and we’ll come and take a look. If you’ve got no heating or hot water right now, our plumbers cover Cardiff around the clock.
