If your boiler will not fire up, the most common causes are low system pressure, a tripped or faulty thermostat, a lockout caused by a fault code, a frozen condensate pipe in cold weather, or an interruption to the gas, power or water supply. Many of these have a simple fix you can check yourself in a few minutes. If the boiler still refuses to start after the basic checks below, it is time to bring in a Gas Safe engineer.
There is never a good time for the heating to pack in. It always seems to happen on the coldest morning of the year, right when you need a hot shower before work. The good news is that a boiler refusing to start does not always mean a big repair bill. Quite often it is something small that has knocked the system off balance. Here is how to work through it calmly, and how to know when the problem is one for the professionals.
Why won’t my boiler turn on at all?
Start with the obvious, because the obvious is right more often than you would think. Check that the boiler still has power and has not tripped the fuse board. Make sure other gas appliances in the house are working, which tells you the gas supply is fine. Then look at your thermostat. If the batteries are flat or the temperature is set below the room temperature, the boiler has no reason to fire. It sounds too simple, but a fresh set of batteries and a nudge of the dial fixes a surprising number of “dead” boilers.
What does low boiler pressure mean and how do I fix it?
Take a look at the pressure gauge on the front of your boiler. It should usually sit between 1 and 1.5 bar when the heating is off. If the needle has dropped into the red or close to zero, the boiler will often refuse to fire as a safety measure. You can usually top the pressure back up yourself using the filling loop underneath the unit, following your manufacturer’s instructions. If the pressure keeps dropping again after you top it up, that points to a leak somewhere in the system, and that is worth getting checked properly rather than topping up every week.
My boiler is showing a fault code. What now?
Modern boilers are clever. When something goes wrong, most will show a fault code on the display and go into what is called lockout, which simply means the boiler has shut itself down to stay safe. Some codes clear with a straightforward reset, and your manual will tell you which ones. If the same code keeps returning, the boiler is trying to tell you there is an underlying issue such as a faulty sensor, a pump problem or an ignition fault. Repeatedly resetting a boiler that keeps locking out is not the answer. That is the moment to pick up the phone.
Could a frozen condensate pipe be the problem?
In winter, absolutely. Your boiler produces a small amount of waste water that drains away through a condensate pipe, and if part of that pipe runs outside, it can freeze solid in a cold snap. When it does, the boiler cannot get rid of the condensate and shuts down, often with a specific fault code and sometimes a gurgling noise. Thawing the pipe gently with a warm cloth or a hot water bottle placed against it will often bring the boiler straight back to life. Never use boiling water, as that can crack the pipe.
When should I stop checking and call an engineer?
If you have checked the power, the gas, the thermostat, the pressure and the condensate pipe and the boiler still will not start, stop there. Anything beyond those basic checks involves the inner workings of a gas appliance, and that is strictly Gas Safe territory. If you can smell gas at any point, do not touch the boiler at all. Turn the gas off at the meter, open the windows, keep flames away and call the emergency gas line straight away.
This is where TLB Plumbing & Heating comes in. As Gas Safe registered engineers based in Bridgend and covering the surrounding areas of South Wales, we are genuine experts in fault finding. We will get to the root of the problem quickly, tell you honestly what needs doing, and get your heating running again. We also offer 24 hour emergency call outs for domestic customers, seven days a week, so a boiler that dies on a Sunday night is not something you have to sit and shiver through. You can see everything we do and book a visit over at tlbplumbingandheating.co.uk.
Frequently Asked Questions
Why does my boiler lose pressure and stop working? A slow drop in pressure usually points to a small leak in the system or a fault with the expansion vessel. Topping the pressure up will get you going again in the short term, but if it keeps falling you should have it investigated so the underlying cause is fixed.
Is it safe to keep resetting my boiler? Resetting once to clear a one off glitch is fine. If your boiler locks out and needs resetting again and again, that is a warning sign of a real fault, and continuing to reset it will not solve anything. Have it looked at by a qualified engineer.
Can I fix a frozen condensate pipe myself? Often yes. Gently warming the outside section of the pipe with a warm cloth or hot water bottle is usually enough to thaw it and restart the boiler. Use warm rather than boiling water to avoid damaging the pipe.
How quickly can TLB Plumbing & Heating get to me? For domestic customers we run emergency call outs 24 hours a day, seven days a week across Bridgend and the wider South Wales area. Get in touch and we will get to you as fast as we can.
