No Hot Water or Heating? Safe Checks First

No Hot Water or Heating? Checks to Try Before You Call an Engineer

If you have no hot water or heating, start with the simple checks: power to the boiler, the boiler pressure, your thermostat and timer, a frozen condensate pipe in cold weather, and credit on a prepayment meter. These fix a surprising number of breakdowns. If none of them work, or anything involves gas, stop and call a Gas Safe registered engineer.

Many boiler problems have simple causes you can check safely in a few minutes, without touching any gas parts. This guide takes you through them in order, says when to stop, and gives typical repair costs.

First: if you smell gas, stop

Before anything else, if you smell gas or suspect a leak:

Do not use light switches, sockets or anything that could make a spark.

Turn off the gas at the meter if you can do so safely.

Open doors and windows.

Leave the property and call the National Gas Emergency number on 0800 111 999.

The same applies if your carbon monoxide alarm goes off, or if anyone has headaches, dizziness or nausea that eases when they leave the house. Do not try to diagnose it yourself.

Never remove the boiler casing or attempt any work on gas parts. Only a Gas Safe registered engineer can legally and safely do that. The checks below only involve controls you are meant to use as a homeowner.

Safe checks to try

1. Check the boiler has power

Is the boiler display lit? If not, check the fused spur switch next to the boiler is on.

Check your consumer unit (fuse box) for a tripped switch. If it trips again straight away, leave it off and call an engineer.

2. Check the boiler pressure

Low boiler pressure is one of the most common reasons for a combi boiler giving no hot water or heating. Look at the pressure gauge on the front of the boiler, or on the display.

Most boilers should sit at around 1 to 1.5 bar when the heating is cold. Check your boiler manual for the right figure.

If it has dropped below about 1 bar, the boiler may lock out to protect itself.

Most boilers can be topped up using the filling loop under the boiler, following the manual. If you are not confident, leave it to an engineer. If the pressure keeps dropping, there is likely a leak or faulty part: look for drips under radiators and the boiler, and call an engineer.

3. Check your thermostat and timer

This catches people out, especially after the clocks change or a power cut.

Is the programmer set to “on” for heating and hot water at the current time?

Is the room thermostat set above the current room temperature? Try turning it up a few degrees.

If you have a wireless or smart thermostat, check the batteries and that it is connected.

Are the radiator valves (TRVs) turned on?

4. Check for a frozen condensate pipe

In freezing weather, this is a very common cause of a boiler not working. Modern condensing boilers drain water through a plastic condensate pipe, which often runs outside. If it freezes, the boiler shuts down and may show a fault code or make a gurgling noise.

To thaw it safely:

Find the pipe, usually a white or grey plastic pipe running from the boiler to an outside drain.

Pour warm, not boiling, water along the pipe, or hold a hot water bottle or warm cloth against it. Boiling water can crack the pipe.

Once it has thawed, reset the boiler.

Only do this if you can reach the pipe safely from the ground, never from a ladder in icy conditions.

5. Reset the boiler

Most modern boilers have a reset button or option. If the display shows a fault or lockout code, check the manual to see what it means, then try a reset once.

If it locks out again, do not keep resetting it. Write down the fault code for the engineer.

6. Check your prepayment meter or gas supply

If you have a prepayment gas meter, check you have credit, including any emergency credit.

If a gas hob is not working either, the problem may be the supply. Contact your energy supplier or, if you suspect a leak, the gas emergency line.

7. If you have hot water but no heating (or the other way round)

This often points to the controls, a diverter valve (combi) or a zone valve (system or regular boiler). Check the timer and thermostat first; if they are fine, call an engineer.

When to stop and call an engineer

Call a Gas Safe registered engineer if:

the pressure keeps dropping or you see water leaking

the boiler locks out repeatedly after a reset

you hear banging, whistling or kettling noises

the pilot light (on older boilers) will not stay lit

the flame looks yellow or orange instead of blue

you see black marks or soot around the boiler

anything involves gas, the flue or the inside of the boiler

If anyone vulnerable is at home, tell the engineer, as many will prioritise urgent jobs.

Typical boiler repair costs

Repair costs depend on the fault, the part, your boiler’s make and whether it is an out-of-hours call. These are typical UK ranges. Prices in Reading and the South East tend to sit at the middle to upper end.

Job

Typical UK range

Notes

Call-out and diagnosis

£60 – £150

Often includes the first 30 to 60 minutes of labour

Out-of-hours or emergency call-out

£100 – £250

Evenings, weekends and bank holidays cost more

Repressurising and minor adjustments

£60 – £150

Usually covered by the call-out charge

Thawing a frozen condensate pipe

£60 – £150

Plus insulation or rerouting if it keeps freezing

Diverter valve replacement

£150 – £400

Common on combi boilers with no hot water

Pump replacement

£200 – £450

Depends on boiler model

Fan replacement

£200 – £450

Depends on boiler model

Gas valve replacement

£150 – £400

Engineer-only; never DIY

Printed circuit board (PCB) replacement

£250 – £600

One of the more expensive repairs

If the repair quote is a large share of the price of a new boiler, or your boiler is well over 10 to 15 years old, it may be worth comparing the cost of a replacement. Our guide to new boiler costs explains the options.

An annual boiler service often picks up worn parts before they fail.

Getting quotes

If you need an engineer, a clear description helps them come prepared and give you a fair price.

Tell them:

your boiler make, model and rough age

exactly what is happening: no heating, no hot water, or both

any fault code on the display

the current boiler pressure

what you have already tried

Ask:

What is your call-out fee, and what does it include?

Do you charge by the hour or a fixed price for the repair?

Do you carry common parts for my boiler, or will you need to order them?

Are you Gas Safe registered for boiler work? (Check their ID card.)

Why three quotes? For a non-urgent repair, comparing three shows you what is fair. Even in an emergency, a couple of quick calls can make a real difference to the price.

You can find local boiler engineers in Reading who handle repairs and breakdowns.

FAQs

Why is my boiler not working?

The most common reasons are low boiler pressure, a thermostat or timer setting, a power problem, a frozen condensate pipe in cold weather, or no credit on a prepayment meter. If simple checks do not fix it, call a Gas Safe registered engineer.

Why does my combi boiler have no hot water but the heating works?

This is often caused by a faulty diverter valve, which switches the combi between heating and hot water. Check your controls first, then call an engineer.

What should I do if my boiler pressure is low?

If the pressure is below about 1 bar, you can usually top it up using the filling loop, following your boiler manual. If it keeps dropping, there is likely a leak or faulty part and you should call an engineer.

Is it safe to reset my boiler?

Yes, using the reset button is safe and designed for homeowners. Try it once. If the boiler keeps locking out, stop and call an engineer.

How much does it cost to fix a boiler with no hot water or heating?

A simple fix may cost around £60 to £150 including the call-out. Replacing a part such as a diverter valve, pump or circuit board typically costs around £150 to £600.

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