No Heating or Hot Water? Causes, Fixes and a New Boiler Tomorrow

Waking up to a cold house and a cold tap is the worst start to a winter day. When you have no heating and no hot water at the same time, the problem is almost always the boiler itself or its gas, power or water supply, rather than the radiators or the hot water cylinder. Here is how to find the cause, what you can safely fix yourself, and what to do if the boiler has had it.

Quick answer

Check the boiler has power, gas and the right pressure (1 to 1.5 bar), turn the thermostat up, then reset it once. In freezing weather, thaw the condensate pipe with warm water. If it still won’t fire up or shows the same fault code, it needs an engineer, or a replacement if it is old.

Common causes of no heating or hot water

1. Low boiler pressure

The most common cause. If the gauge is below 1 bar, the boiler locks out to protect itself. Top it up using the filling loop under the boiler until it reads about 1.5 bar, close the valves, then reset. If it keeps dropping, there is a leak somewhere that needs finding. Read our boiler pressure guide.

2. Frozen condensate pipe

In a cold snap, the plastic pipe that drains water from a condensing boiler can freeze, and the boiler shuts down. You may hear gurgling. Pour warm water (not boiling) along the outside pipe, then reset the boiler. Full frozen condensate pipe guide.

3. No gas reaching the boiler

Check your gas hob works and, if you have a prepayment meter, that it has credit. If other gas appliances work, the boiler may have an ignition fault (often shown as a fault code such as F28 on a Vaillant or EA on a Worcester).

4. No power or a tripped switch

A blank display means no power. Check the fused spur switch next to the boiler and your fuse box.

5. Thermostat, timer or controls

A flat thermostat battery or a timer reset after a power cut can stop both heating and hot water on a combi. Turn the thermostat up and check the clock.

6. Failed part: pump, fan, diverter valve or PCB

If the boiler fires but nothing gets hot, or it shows a fault code that comes back after a reset, a part has probably failed. On a boiler over 10 years old, the repair can cost a large chunk of the price of a new one.

What your fault code means

Look up the code on your display: Vaillant, Worcester Bosch, Baxi, Ideal, or see all boiler error codes.

Repair or replace?

A new boiler usually makes more sense when the boiler is over 10 to 12 years old, it has broken down more than once this year, parts are hard to get, or the repair quote is several hundred pounds. A new A-rated gas boiler also uses less gas than an old one.

FAQs

Why do I have no heating or hot water but the boiler has power?

The most likely causes are low pressure, a frozen condensate pipe, a gas supply problem or a failed part. Check the display for a fault code.

Is it safe to reset my boiler?

Yes, pressing reset once or twice is safe. If it locks out again, stop and get a Gas Safe engineer to look at it. Never open the casing yourself.

How quickly can I get a new boiler?

Order online by 3pm and we can fit your new gas boiler the next day, 7 days a week. Prices start from £1,790 supplied and fitted, with a guarantee of up to 14 years depending on model.