What is the first thing to check when there is no heating or hot water?

Look at the boiler display. A code or flashing light tells you it has locked out and roughly why. If the display is blank, check the power at the fused spur and the consumer unit. If it is lit with no code, check the gas by lighting a hob and the pressure gauge.

Why do I suddenly have no heating or hot water?

The sudden causes are usually a boiler lockout, a gas supply interruption or prepayment meter running out, a tripped electrical supply, a frozen condensate pipe in cold weather, or pressure that has dropped below what the boiler will run on. Each can be checked in a few minutes.

How long can a landlord leave you without heating or hot water?

There is no single fixed number of hours in law, but loss of heating and hot water is treated as an urgent repair, and landlords are expected to act promptly, particularly in cold weather or where someone vulnerable lives in the property. Report it in writing and keep a record of when you did.

Can a power cut stop my heating and hot water?

Yes, while it lasts, because the boiler needs electricity for its fan, pump and controls. When power returns, the programmer may have lost its time, so check the clock and schedule. Some boilers lock out after a power interruption and need a single reset.

Is it the boiler or the thermostat?

If the boiler display shows a fault or the boiler will not fire even when you turn the heating to constant and the thermostat right up, it is the boiler. If the boiler fires for hot water but not when the thermostat calls, the thermostat or its batteries are the more likely cause.

Should I keep topping up the boiler pressure?

Once is fine. If the pressure keeps dropping, stop topping up and get the leak found. Constant refilling adds oxygen and fresh water to the system, which speeds up corrosion inside radiators and the boiler.

No Heating or Hot Water? What Has Failed and What to Do

When the heating and the hot water fail together, the cause is almost always something both depend on: the gas supply, the electricity to the boiler, the system pressure, a frozen condensate pipe, or the boiler itself having locked out. Losing only one of the two points at a valve or a control; losing both points upstream, at the boiler or what feeds it. Check the boiler display for a code, light a hob to prove the gas, check the fused spur and the pressure gauge, and look at the condensate pipe if it is freezing outside. If all of that is fine and the boiler still will not fire, it needs a Gas Safe engineer, and if you have a hot water cylinder with an immersion heater you can have hot water again within the hour while you wait.

Why losing both at once narrows it down

Your heating and hot water share one heat source, the boiler, and the boiler shares its gas, its power and its water pressure with nothing else in the house. So when both stop together, the fault is rarely in the radiators or the taps. It is in the boiler or in one of the three things the boiler needs to run.

That is good news, because the first round of checks is short and costs nothing. It is also why the question an engineer asks first on the phone is what the boiler is showing, not what the radiators are doing.

If you only have one of the two problems, you are in a different situation. Heating working with no hot water usually means a diverter valve, a motorised valve or a cylinder thermostat, and our no hot water but heating works guide covers that. Hot water with no heating tends to be a room thermostat, a pump or a zone valve.

Check these first, in this order

Work down the list. Each step takes a minute and rules out a whole group of causes.

The boiler display. A code or flashing light means a lockout. Write the code down, then try one reset.
The gas. Light a hob. No gas at the hob means a supply problem, a meter valve turned off, or a prepayment meter out of credit.
The electricity. Is the boiler display lit at all? Check the fused spur switch beside the boiler and the breaker for it in the consumer unit.
The pressure gauge. Below about 1 bar with the system cold, most sealed boilers will not run. Top up through the filling loop as the manual describes.
The condensate pipe. In freezing weather the plastic pipe running outside can ice up and lock the boiler out. Pour warm water, not boiling, along it and reset.
The controls. A programmer that lost its time in a power cut, or a wireless thermostat with flat batteries, can leave a healthy boiler with nothing asking it to run.

When the boiler has locked out

A lockout is the boiler protecting itself. It has tried to light, or run, and found something wrong: no flame after ignition, overheating, low pressure, a fan or flue problem. It shuts down and waits. Heating and hot water stop together because the boiler provides both.

One or two resets are reasonable, particularly after a gas or power interruption, which can cause a one off lockout. If it locks out again, stop. The cause is still there and further resets only hide the pattern an engineer needs to see. If yours is a Worcester Bosch, our guide to a Worcester boiler flashing blue light explains the common lockouts on those models.

How to get hot water back tonight

If you have a hot water cylinder, look for an immersion heater. It is an electric element in the cylinder, usually with its own switch on the wall nearby, often labelled. Switching it on heats the stored water without the boiler at all, and within an hour or so you have enough for washing and a bath or shower. It is slower and dearer to run than gas, so switch it off again once the boiler is repaired.

If you are on a combi boiler there is no stored water and no immersion heater, so the options are the kettle and an electric shower if you have one. For heating, portable electric heaters bridge the gap. Oil filled radiators are the safer choice in a bedroom and for anyone vulnerable.

Never try to heat the house with a gas hob or oven left on, and do not use outdoor heaters or barbecues indoors. Both are carbon monoxide risks.

Faults that need an engineer

If the gas, power, pressure and condensate are all fine and the boiler still will not fire, the fault is inside the appliance or in the wiring of the controls. The usual culprits are the ignition electrode, the gas valve, the fan, the printed circuit board, a failed pump on a system boiler, or a sensor reporting a false reading. Each has its own test, and a proper diagnosis measures rather than guesses.

A pressure that keeps falling is its own problem. If you top the boiler up and it is back below 1 bar within a day or two, water is escaping somewhere: a weeping radiator valve, a joint under a floor, or the boiler pressure relief valve discharging outside. Topping up repeatedly without finding the leak brings fresh oxygen into the system and speeds up corrosion. Our leak detection and repair service is for exactly that situation.

Work inside a gas boiler must by law be done by a Gas Safe registered engineer. If you smell gas at any point, turn the supply off at the meter, open windows and call the gas emergency line on 0800 111 999.

Is no heating or hot water an emergency?

It is treated as urgent, and more so for a household with a baby, an elderly person, someone unwell, or in a cold spell. It is a genuine emergency if there is a gas smell, water escaping from the boiler or pipework, or the boiler making loud banging or boiling noises, because those are safety or damage risks rather than comfort problems.

If you rent, the repair is your landlord or managing agent to arrange. Report it in writing straight away with photos of the boiler display. Our guide to landlord hot water responsibilities explains what a landlord is expected to do and how quickly.

Getting it fixed

If the checks above have not brought the boiler back, call us or send an enquiry with the boiler make and model and any code it is showing. We have 20 engineers covering London, and a no heating and no hot water call is one we prioritise. Our rate is published on the pricing page and agreed with you before anyone attends.

Questions we get asked

What is the first thing to check when there is no heating or hot water?: Look at the boiler display. A code or flashing light tells you it has locked out and roughly why. If the display is blank, check the power at the fused spur and the consumer unit. If it is lit with no code, check the gas by lighting a hob and the pressure gauge.
Why do I suddenly have no heating or hot water?: The sudden causes are usually a boiler lockout, a gas supply interruption or prepayment meter running out, a tripped electrical supply, a frozen condensate pipe in cold weather, or pressure that has dropped below what the boiler will run on. Each can be checked in a few minutes.
How long can a landlord leave you without heating or hot water?: There is no single fixed number of hours in law, but loss of heating and hot water is treated as an urgent repair, and landlords are expected to act promptly, particularly in cold weather or where someone vulnerable lives in the property. Report it in writing and keep a record of when you did.
Can a power cut stop my heating and hot water?: Yes, while it lasts, because the boiler needs electricity for its fan, pump and controls. When power returns, the programmer may have lost its time, so check the clock and schedule. Some boilers lock out after a power interruption and need a single reset.
Is it the boiler or the thermostat?: If the boiler display shows a fault or the boiler will not fire even when you turn the heating to constant and the thermostat right up, it is the boiler. If the boiler fires for hot water but not when the thermostat calls, the thermostat or its batteries are the more likely cause.
Should I keep topping up the boiler pressure?: Once is fine. If the pressure keeps dropping, stop topping up and get the leak found. Constant refilling adds oxygen and fresh water to the system, which speeds up corrosion inside radiators and the boiler.