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About

Contact

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BOILER FAULTS

No hot water,
or no heating?

Which one of the two you have lost is the most useful diagnostic there is. It usually points at the part before anyone opens the boiler.

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Gas Safe registeredEvery engineer on the job

Approved InstallerExtended manufacturer warranties

Get your hot water back

THE SHORT ANSWER

Heating fine but no hot water usually means the diverter valve. Hot water fine but no heating usually means the pump or a motorised valve. Neither working usually means pressure, ignition or the PCB.

On a combi the same boiler does both jobs, so losing only one of them tells you the fault is in the part that chooses between them rather than in the boiler itself. That is why the first question we ask on the phone is not what make it is, it is which of the two you have still got. Get that right and you have narrowed a callout down to a handful of parts before anyone gets in the van.

NARROWING IT DOWN

What you can check, and what it points at.

Five minutes with this list saves you paying somebody to tell you the thermostat batteries were flat.

Check these first

Two minutes, no tools

Pressure gauge

Should read 1 to 1.5 bar cold

Fault code

Photograph it before resetting

Room thermostat

Batteries in, set above room temperature

Timer or programmer

Not reverted after a power cut

Other gas appliances

Do they light

Condensate pipe

In cold weather, is it frozen

What each points at

Before anyone opens anything

Heating only

Diverter valve, usually stuck

Hot water only

Pump, motorised valve or controls

Neither, low pressure

Leak, relief valve or expansion vessel

Neither, code showing

Ignition, fan, flue or PCB

Neither, cold snap

Frozen condensate, most likely

Intermittent

Hardest to find. Note times and codes

THE THREE PATTERNS

What each pattern usually means.

Heating works, no hot water

Most often the diverter valve, the part that sends hot water either to the taps or to the radiators. They stick, usually in the heating position, which is why the radiators carry on working. It is a common and generally straightforward repair on most combis.

Hot water works, no heating

Usually the pump, a motorised valve, or the room thermostat rather than the boiler. Before calling anyone, check the thermostat has battery and is calling for heat, and check the timer has not reverted after a power cut, because both happen more than you would think.

Neither works

Start with the pressure gauge and any fault code. Low pressure and a frozen condensate in winter cover a large share of these. If pressure is fine and there is a code on the display, photograph it and call, because that is the boiler telling you exactly where to look.

WHAT TO EXPECT

What is likely, and what it means for you.

Heating fine, no hot water

Usually the diverter valve.

A common combi fault and generally a straightforward repair on a boiler that is not too old. It is the part that decides whether hot water goes to the taps or the radiators, and it tends to stick in the heating position.

Hot water fine, no heating

Often not the boiler at all.

Pump, motorised valve, or the controls. Before booking anyone, put fresh batteries in the room thermostat and turn it well up. It is a surprisingly common cause and it costs you nothing to rule out.

Neither, and the pressure is low

Top it up once, then watch it.

Bring it to about 1.5 bar cold on the filling loop and see whether it holds. If you are doing that every week, the problem is not the pressure, it is where the water is going.

Neither, and there is a code

Photograph it and call.

The code is the most useful thing you have. It often tells us the part to bring, which turns two visits into one. Send it with the make and model when you message.

COMMON QUESTIONS

Questions we get asked.

Why do I have heating but no hot water?

Why do I have hot water but no heating?

My boiler has no hot water and no heating. What should I check?

Is a diverter valve worth repairing?

How quickly can you come out?

Will you tell me what it costs before you come?

Lost your hot water or your heating?

Tell us which one you have lost and the make of the boiler. That usually gets us to the likely fault before we set off, and you get the price first.

BOILER SERVICING

GAS SAFETY (CP12)

HEATING & PLUMBING

LANDLORD PACKAGES

GOT A PLUMBING OR HEATING JOB IN BRIDGEND?

Get your hot water back

testimonials

Real customers. Real results.

213 five star reviews from homeowners across South Wales. Every one of them left on Google, not written by us.

David Rees

August 2026

★★★★★

An outstanding Gas Engineer and a fine individual. I cannot recommend LMB Plumbing & Heating highly enough. He installed a new Gas Boiler and overhauled our 25 year old Central Heating system for a good price.

LMB REPLIED

Thank you, David — we’re delighted to hear you had such a positive experience. We're glad the new gas boiler installation and overhaul of your…

Lee Major

July 2026

★★★★★

I can’t recommend Lloyd highly enough. From the initial Contact right through to completion of the job , his customer service was outstanding. Lloyd arrived exactly on time, was polite , friendly and professional throughout. The quality of his workmanship was excellent and he clearly takes great…

LMB REPLIED

Thank you so much, Lee, for your fantastic review and for recommending Lloyd. We’re delighted he arrived on time, was professional and friendly, and…

Dafydd Pugh

July 2026

★★★★★

Excellent. Lloyd provided an excellent service - good communication, timely arrival, left the work area clean and did the work efficiently

LMB REPLIED

Thank you Dafydd

Nigel Walters

July 2026

★★★★★

LMB responded the same day to repair a gas problem I had. Other companies I contacted were unhelpful, and most of them actually declined the work. LMB were positive & engaging from the start, fixed the problem and charged a fair price. Highly recommended, ask for Lloyd.

LMB REPLIED

Appreciate the feedback Nigel, pleasure to do work for.

Scott Rivers

July 2026

★★★★★

LMB plumbing & Heating have been fantastic since first conversation / quote to boiler install. From boiler install we had him come back to fit our shower room and the standard and service is second to none. If I could give more stars I would. Class from the lads at LMB plumbing & Heating

LMB REPLIED

Thankyou Scott, pleasure fitting the boiler and heating system for you!

Samantha

July 2026

★★★★★

I have had these gentlemen come to my property on two separate occasions. Very prompt, very polite and got the job done. I even contacted them late on Sunday evening and they politely arranged for a next day appointment, came and solved the problem. Will always use and recommend!

LMB REPLIED

Thank you so much for your wonderful review, Samantha. We're thrilled our team was prompt, polite, and able to resolve your issue quickly on short…

Craig Williams

July 2026

★★★★★

Lloyd recently fitted our new boiler. It has been fitted to a very high standard and he took care of the house when working. Polite and punctual.

LMB REPLIED

Thank you, Craig, for the excellent review. We're delighted Lloyd fitted your new boiler to such a high standard and took good care of your home. We…

Rachel 01

June 2026

★★★★★

Lloyd came out and quoted a job for us, to change our bath, sink, & toilet. He has been brilliant from start to finish I’m so glad my mum recommended him. He was incredibly professional and nothing was too much trouble. Will most certainly have him back to do future work and will 100% recommend him…

LMB REPLIED

Thank you so much, Rachel, for the wonderful review and for recommending us to your mum. I’m delighted the bathroom, sink, and toilet work met your…

David Rees

August 2026

★★★★★

LMB REPLIED

Thank you, David — we’re delighted to hear you had such a positive experience. We're glad the new gas boiler installation and overhaul of your…

Lee Major

July 2026

★★★★★

LMB REPLIED

Thank you so much, Lee, for your fantastic review and for recommending Lloyd. We’re delighted he arrived on time, was professional and friendly, and…

Dafydd Pugh

July 2026

★★★★★

Excellent. Lloyd provided an excellent service - good communication, timely arrival, left the work area clean and did the work efficiently

LMB REPLIED

Thank you Dafydd

Nigel Walters

July 2026

★★★★★

LMB REPLIED

Appreciate the feedback Nigel, pleasure to do work for.

Scott Rivers

July 2026

★★★★★

LMB REPLIED

Thankyou Scott, pleasure fitting the boiler and heating system for you!

Samantha

July 2026

★★★★★

LMB REPLIED

Thank you so much for your wonderful review, Samantha. We're thrilled our team was prompt, polite, and able to resolve your issue quickly on short…

Craig Williams

July 2026

★★★★★

Lloyd recently fitted our new boiler. It has been fitted to a very high standard and he took care of the house when working. Polite and punctual.

LMB REPLIED

Thank you, Craig, for the excellent review. We're delighted Lloyd fitted your new boiler to such a high standard and took good care of your home. We…

Rachel 01

June 2026

★★★★★

LMB REPLIED

Thank you so much, Rachel, for the wonderful review and for recommending us to your mum. I’m delighted the bathroom, sink, and toilet work met your…

ADVICE

Thirty guides,written by our team

Boilers, radiators, gas certificates, and what the jobs actually cost.

Worcester, Baxi or Vaillant?

Build quality, warranties, and what each one costs fitted.

boilers
buying

How much is a new boiler in Bridgend?

From £1,900 fitted, and what moves the price up or down.

costs
bridgend

What does a boiler service cost?

£84, what gets checked, and why skipping it voids your warranty.

costs
servicing

Landlord gas safety (CP12) in Wales

The annual legal duty, and how to do it in one visit.

landlords
legal

Boiler losing pressure?

What to check yourself, and when to stop and call.

fixes
boilers

Radiators not heating up

Cold at the top, cold at the bottom, and what each means.

fixes
radiators

ADVICE

Thirty guides,written by our team

Boilers, radiators, gas certificates, and what the jobs actually cost.

Worcester, Baxi or Vaillant?

Build quality, warranties, and what each one costs fitted.

boilers
buying

How much is a new boiler in Bridgend?

From £1,900 fitted, and what moves the price up or down.

costs
bridgend

What does a boiler service cost?

£84, what gets checked, and why skipping it voids your warranty.

costs
servicing

Landlord gas safety (CP12) in Wales

The annual legal duty, and how to do it in one visit.

landlords
legal

Boiler losing pressure?

What to check yourself, and when to stop and call.

fixes
boilers

Radiators not heating up

Cold at the top, cold at the bottom, and what each means.

fixes
radiators

ADVICE

Thirty guides,written by our team

Boilers, radiators, gas certificates, and what the jobs actually cost.

Worcester, Baxi or Vaillant?

Build quality, warranties, and what each one costs fitted.

boilers
buying

How much is a new boiler in Bridgend?

From £1,900 fitted, and what moves the price up or down.

costs
bridgend

What does a boiler service cost?

£84, what gets checked, and why skipping it voids your warranty.

costs
servicing

Landlord gas safety (CP12) in Wales

The annual legal duty, and how to do it in one visit.

landlords
legal

Boiler losing pressure?

What to check yourself, and when to stop and call.

fixes
boilers

Radiators not heating up

Cold at the top, cold at the bottom, and what each means.

fixes
radiators

BEFORE YOU GO

Keep reading.

More of the same, written by the engineers who do the work.

READ THIS FIRST

What a new boiler actually costs

Real fitted prices, what pushes them up, and the three lines to check in any quote.

Read it

→

OTHER SERVICES

New boiler installation

→

Boiler servicing

→

Boiler repair

→

Gas engineer

→

WORTH A READ

Worcester vs Baxi vs Vaillant vs Ideal

→

How to reset a boiler

→

Cold radiators explained

→

Boiler losing pressure

→

No hot water,or no heating?

No hot water,or no heating?

No hot water,or no heating?

Heating fine but no hot water usually means the diverter valve. Hot water fine but no heating usually means the pump or a motorised valve. Neither working usually means pressure, ignition or the PCB.

Heating fine but no hot water usually means the diverter valve. Hot water fine but no heating usually means the pump or a motorised valve. Neither working usually means pressure, ignition or the PCB.

Heating fine but no hot water usually means the diverter valve. Hot water fine but no heating usually means the pump or a motorised valve. Neither working usually means pressure, ignition or the PCB.

What you can check, and what it points at.

What you can check, and what it points at.

What you can check, and what it points at.

Check these first

Check these first

What each points at

What each points at

What each pattern usually means.

What each pattern usually means.

What each pattern usually means.

Heating works, no hot water

Heating works, no hot water

Hot water works, no heating

Hot water works, no heating

Neither works

Neither works

What is likely, and what it means for you.

What is likely, and what it means for you.

What is likely, and what it means for you.

Usually the diverter valve.

Usually the diverter valve.

Usually the diverter valve.

Often not the boiler at all.

Often not the boiler at all.

Often not the boiler at all.

Top it up once, then watch it.

Top it up once, then watch it.

Top it up once, then watch it.

Photograph it and call.

Photograph it and call.

Photograph it and call.

Questions we get asked.

Questions we get asked.

Questions we get asked.

Why do I have heating but no hot water?

Why do I have hot water but no heating?

My boiler has no hot water and no heating. What should I check?

Is a diverter valve worth repairing?

How quickly can you come out?

Will you tell me what it costs before you come?

Lost your hot water or your heating?

testimonials

Real customers. Real results.

Thirty guides,written by our team

Thirty guides,written by our team

Thirty guides,written by our team

Keep reading.

Keep reading.

Keep reading.

What a new boiler actually costs

What a new boiler actually costs

What a new boiler actually costs

OTHER SERVICES

WORTH A READ

No hot water,
or no heating?

No hot water,
or no heating?

No hot water,
or no heating?