Woken up to no heating or hot water? Work through these before calling anyone. A meaningful proportion of apparent breakdowns are on this list.
If none of them fixes it, the sections further down cover the faults that need an engineer.
Six checks, five minutes
1. The boiler display. Is there an error code? Note it, and look it up in our boiler error codes guide. Blank screen suggests a power problem. A flashing flame symbol means it is trying to ignite. Check the pressure reading while you are there.
2. Power supply. Is the boiler switched on at the wall? Has a fuse or breaker tripped? Do other appliances work, in case there is a wider power cut? Has the timer been knocked?
3. Boiler pressure. The most common cause of a shutdown. It should read 1 to 1.5 bar. Below 1 and it will not fire. Top up using the filling loop under the boiler. This is a safe, easy job to do yourself, and our guide to a boiler losing pressure walks through it.
4. Gas supply. Do other gas appliances work, such as a hob? If it is a prepay meter, is there credit? Has the emergency control valve been turned off?
If you smell gas at any point, do not touch any switches or use a naked flame. Leave the property and call the National Gas Emergency Service on 0800 111 999.
5. Thermostat. Turned up above the current room temperature? Batteries good in a wireless one? Not set to off or summer mode? AM and PM correct on the timer?
6. Frozen condensate. Very common in cold weather. If it is below freezing outside, find the white plastic pipe running outside and pour warm, not boiling, water over it. Reset afterwards.
Then try a reset
If the checks have not turned up an obvious cause, try a reset. Find the reset button, usually marked with a flame symbol. Hold it for three to five seconds and wait one to two minutes for the boiler to attempt ignition, listening for it firing up.
If it does not stay running after two or three attempts, stop. Repeated resets without addressing the underlying cause can cause damage. Call an engineer.
Heating works but no hot water
On a combi: most likely a diverter valve fault, or a flow sensor not detecting demand. Check hot water has not been turned off at the boiler controls. If it has not, both of those faults need an engineer.
On a system boiler with a cylinder: check the cylinder thermostat is turned up. A stuck motorised valve is the other common cause, and that also needs an engineer. If you have an immersion heater, it will get you through in the meantime.
Hot water at some taps but not others
That is plumbing rather than the boiler. Usually an airlock, which is common after plumbing work, a faulty thermostatic mixer valve in a shower or tap, or scale blocking the hot supply to that outlet.
Call immediately if
- You smell gas anywhere
- The boiler is leaking water
- There is loud banging or kettling
- There are black marks or soot around the boiler
- The flame is yellow or orange rather than blue
- An error code will not clear after a reset
- There is a burning smell
The same applies if you have worked through every check above and still have no heating or hot water. At that point it is a boiler repair for a Gas Safe engineer, not something to keep trying yourself.
Staying warm while you wait
Portable electric heaters warm one room quickly, and concentrating on one room is more efficient than trying to heat the house. Layer clothing rather than wearing one thick layer: several thin layers hold heat better, and warm socks and slippers make a real difference. Hot drinks and hot water bottles genuinely help. Keep internal doors closed and use draught excluders to hold heat in the rooms you are using.
Preventing the next one
An annual service is the single most effective thing. The engineer checks every component, cleans the burner and heat exchanger, tests the safety devices, and identifies worn parts before they fail. It also keeps the boiler running efficiently, which saves you money. It costs a fraction of an emergency call-out and it is what keeps your guarantee valid. A boiler service costs from £105.
Frequently asked
Is no heating an emergency?
It depends who is in the house. In winter, with young children, elderly residents or anyone with a health condition, we treat it as a priority. For a healthy adult household in mild weather it can usually wait until the next working day.
How many times can I reset the boiler?
Two or three. If it will not stay running after that, stop. Repeated resets without addressing the cause can damage components and will not fix whatever the safety device detected.
Why is there heating but no hot water?
On a combi, usually a diverter valve. On a system boiler, a cylinder thermostat or a stuck motorised valve. The boiler is working, it is just not sending the heat where you want it.