No Hot Water but Heating Works? Common Causes and What to Do
Your radiators are getting warm, your central heating seems to be working normally, but when you turn on the hot tap, the water stays cold.
It's a frustrating problem, particularly when you need a hot shower or you're trying to get the family ready in the morning.
The good news is that heating working but no hot water doesn't automatically mean you need a new boiler. There are several possible explanations, ranging from incorrect settings to a faulty internal component.
At Plumb Rite, our Gas Safe registered heating engineers have over 35 years of experience helping homeowners with boiler and central heating problems across Kingswinford, Dudley, Stourbridge, Brierley Hill and Halesowen.
In this guide, we'll explain why your heating may work while your hot water doesn't, what you can safely check yourself and when to contact a professional.
Key Takeaways: Why Do I Have Heating but No Hot Water?
If your central heating works but you have no hot water, the cause depends on your boiler and hot-water system.
On a combi boiler, possible causes include a faulty diverter valve, a problem detecting hot-water demand or a blocked plate heat exchanger. On systems with a hot-water cylinder, the problem may involve the programmer, cylinder thermostat, motorised valve or immersion heater.
Before calling an engineer, you can safely check your boiler display, hot-water settings, water flow and whether the problem affects every tap.
However, never remove your boiler casing or attempt internal boiler repairs yourself. A qualified professional should investigate persistent faults.
Why Is My Central Heating Working but My Hot Water Isn't?
Your central heating and domestic hot water are related, but they don't always operate in exactly the same way. Depending on your heating system, different controls and components manage the water going to your radiators and the hot water supplied to your taps.
This means one function can continue working while the other develops a fault.
For example:
Your radiators might heat normally, but your combi boiler may not respond when you open a hot tap.
Your boiler may heat the radiators, but a faulty control could prevent your hot-water cylinder from heating.
You might have hot water at the kitchen tap but not in the shower, suggesting a problem with the shower rather than the boiler.
Identifying which of these situations applies can help narrow down the cause.
7 Common Reasons You Have No Hot Water but the Heating Works
1. Faulty Diverter Valve on a Combi Boiler
A faulty diverter valve is one possible explanation when a combi boiler provides central heating but no hot water.
A combi boiler supplies hot water directly to your taps without needing a separate hot-water storage cylinder.
Many combi boilers use a diverter valve to direct heat towards either your central heating or domestic hot water. When you open a hot tap, the boiler should respond to that demand.
If the diverter valve becomes stuck or fails, the boiler may continue heating your radiators but struggle to provide hot water.
Possible signs include:
Radiators heating normally while taps remain cold
Hot water working intermittently
Water becoming warm but never reaching the expected temperature
The boiler failing to switch properly between heating and hot water
What should you do?
A faulty diverter valve needs professional diagnosis. Don't attempt to access or repair the valve yourself.
A Gas Safe registered heating engineer can check whether the diverter valve is responsible or whether another component is causing similar symptoms.
2. The Boiler Isn't Detecting Hot-Water Demand
When you open a hot tap on a combi boiler, the appliance needs to detect that water is flowing. Depending on the model, it may use a flow sensor, turbine or another component to recognise the demand.
If this component fails, the boiler may not realise that you're asking for hot water.
Possible signs include:
No hot water from multiple taps
Central heating operating normally
The boiler not responding when a hot tap is opened
Intermittent hot-water operation
If the boiler display normally shows a tap symbol when hot water is running, check whether that symbol appears. The meaning of display symbols varies by manufacturer, so consult your boiler manual.
If the boiler isn't responding to hot-water demand, arrange a professional inspection.
3. Blocked or Scaled Plate Heat Exchanger
Many combi boilers use a plate heat exchanger to transfer heat into the water supplied to your taps. Over time, limescale or debris can restrict heat transfer or water flow.
This may cause:
Hot water that alternates between warm and cold
Reduced hot-water performance
Water that never becomes properly hot
Boiler fault codes or unusual operating behaviour
A blocked heat exchanger isn't something homeowners should attempt to clean themselves. A heating engineer can determine whether cleaning or replacing a component is appropriate.
It's also worth remembering that not every hot-water problem is caused by sludge in the central heating system. Power flushing and domestic hot-water faults are different issues, so the cause should be diagnosed before recommending treatment.
If you're also experiencing cold radiators or poor heating circulation, read our guide: What Is a Power Flush? Signs Your Central Heating System Needs One.
4. Incorrect Hot-Water Settings or Controls
Sometimes the explanation is less complicated. Before assuming an internal component has failed, check that your boiler's hot-water function is enabled and that the settings are appropriate.
On some boilers, hot-water temperature can be adjusted separately from central heating temperature. If you have a hot-water cylinder, check that your programmer is set to heat water when needed.
Safe checks include:
Is the hot-water function enabled?
Is the hot-water temperature set appropriately?
Is the programmer or timer correctly configured?
Does the boiler display an error message?
Have any settings recently been changed?
Always follow the manufacturer's instructions. Avoid changing unfamiliar installer or service settings.
5. Faulty Motorised Valve or Cylinder Controls
If you have a system boiler or conventional boiler with a separate hot-water cylinder, the cause may be different from a combi boiler fault.
These systems can use motorised valves, thermostats and programmers to control heating and hot water independently.
If a motorised valve isn't operating correctly, your radiators may heat while your hot-water cylinder remains cold. A faulty cylinder thermostat or programmer may produce similar symptoms.
Signs to look out for include:
Central heating works but the hot-water cylinder doesn't heat
The hot-water schedule appears correct, but the water remains cold
Hot water is available only occasionally
The cylinder isn't reaching its usual temperature
You can check the accessible programmer settings, but electrical testing and valve repairs should be carried out by an appropriately competent professional.
Where work involves the gas boiler or gas-related components, use a Gas Safe registered engineer.
6. Low Water Flow or a Problem at One Tap
Not every hot-water problem starts at the boiler. If the hot water works in your kitchen but not in your bathroom, the issue could involve a particular tap, shower mixer or local plumbing component.
For example, a faulty thermostatic shower mixer may prevent the shower from delivering hot water even though the boiler is working correctly.
Try this simple check:
Turn on the hot tap in your kitchen, then test another hot tap elsewhere in the house. If the problem only affects one outlet, tell your plumber or heating engineer. This information can help avoid unnecessary boiler investigations.
7. Boiler Pressure, Fault Codes or an Intermittent Boiler Fault
Although low boiler pressure often affects both heating and hot water, it is still worth checking the pressure gauge if your boiler has one.
Some boilers may continue operating in certain circumstances while displaying a warning or developing an intermittent fault.
For many sealed central heating systems, a cold pressure reading of approximately 1–1.5 bar is common, but the correct range depends on the appliance and manufacturer's instructions.
If your boiler is showing a fault code, make a note of it before contacting an engineer.
You can also read our related guide: Why Does My Boiler Keep Switching Off? Common Causes and What to Do.
No Hot Water but Heating Works: Quick Troubleshooting Guide
The symptoms can offer useful clues, although they cannot confirm the fault without proper testing.
What you're experiencing | Possible explanation | Recommended action |
Radiators hot, all taps cold | Diverter valve or hot-water demand fault on a combi | Check settings and arrange diagnosis |
Hot water alternates between hot and cold | Heat exchanger, sensor or flow issue | Contact a heating engineer |
Boiler doesn't respond when a hot tap opens | Hot-water demand sensor or flow problem | Check display, then book inspection |
Hot water works at one tap but not another | Tap or shower mixer problem | Check affected outlet |
Heating works, but hot-water cylinder stays cold | Programmer, thermostat or motorised valve | Check accessible controls and seek professional help |
Boiler displays a fault code | Appliance-specific fault | Record the code and follow the manual |
Important: These are possible causes, not a remote diagnosis. Several faults can produce the same symptoms.
What Can You Safely Check Before Calling a Heating Engineer?
If your heating is working but your hot water isn't, there are a few straightforward checks you can make without opening the boiler or disturbing any internal components.
Check 1: Test More Than One Hot Tap
Run the hot water at your kitchen sink and another tap.
If every hot tap is cold, the problem is more likely to involve the hot-water supply or heating appliance.
If only one tap or shower is affected, the issue may be local to that fixture.
Check 2: Check Your Boiler Display
Look for:
Error or fault codes
Warning lights
A hot-water demand symbol
Unusual readings
Write down any fault code so you can explain it to the engineer.
Check 3: Check Hot-Water Settings
Make sure the hot-water function is switched on.
If your system has a programmer or separate hot-water controls, check the schedule and settings.
Check 4: Look at Boiler Pressure
If your boiler has a pressure gauge, compare the reading with the manufacturer's recommended range.
Don't repeatedly repressurise a system that keeps losing pressure.
Check 5: Check Whether the Problem Is Intermittent
Does the hot water:
Never heat up?
Become warm and then cold?
Work at some times but not others?
Stop when another tap is opened?
These details are useful when diagnosing the problem.
Check 6: Follow the Manufacturer's Instructions
Some boilers allow a user reset after a temporary fault.
Only reset the boiler if the manufacturer's instructions recommend doing so for the displayed fault. If the fault returns, arrange an inspection rather than repeatedly resetting it.
Never remove the boiler casing, work on gas components or attempt internal electrical repairs.
Is It Safe to Use the Heating If You Have No Hot Water?
If your central heating is working normally but the taps are cold, this doesn't automatically indicate a dangerous boiler fault.
However, the cause is unknown until the system has been assessed.
If there are no warning signs, you can contact a qualified engineer for advice about continued use.
Stop using the appliance and seek urgent assistance if you notice:
A smell of gas
A carbon monoxide alarm activating
Signs of overheating or scorching
A significant water leak affecting the appliance or electrics
Any other indication that the appliance may be unsafe
If you suspect a gas leak in Great Britain, leave the property, avoid flames and electrical switches, and call the National Gas Emergency Service on 0800 111 999 from a safe location.
If a carbon monoxide alarm activates, get everyone into fresh air, seek urgent advice and do not re-enter until it is safe. Call 999 if anyone is seriously unwell.
Can a Boiler Service Fix a Hot-Water Problem?
A routine boiler service and a boiler repair are not the same thing.
A service is primarily intended to check the appliance's condition, operation and safety, following the manufacturer's servicing requirements.
If your hot water has already stopped working, you may need a boiler fault diagnosis and repair, rather than a standard annual service.
However, regular servicing can help identify developing problems and maintain the boiler in accordance with the manufacturer's recommendations.
Plumb Rite provides both boiler repairs in Kingswinford and annual boiler servicing.
Should You Repair or Replace a Boiler That Has No Hot Water?
Not necessarily. A boiler that still heats your radiators but fails to supply hot water may have a repairable component fault.
Whether repair or replacement is the better option depends on factors such as:
The age and condition of the boiler
The cause of the fault
The cost of replacement parts and labour
The availability of suitable components
Previous breakdowns
The overall condition and suitability of the heating system
For a relatively modern boiler in otherwise good condition, a repair may be the sensible choice. For an older boiler with repeated faults or expensive repairs, replacement may deserve consideration.
If you're unsure, our guide to Should I Repair or Replace My Boiler? explains the factors to consider. Plumb Rite can assess the problem and discuss the appropriate options. If a replacement is necessary, we also provide new boiler installation in Kingswinford.
Boiler Repairs for No Hot Water in Kingswinford and Surrounding Areas
Losing hot water is inconvenient at any time of year, especially when your household relies on the boiler for everyday washing and bathing.
At Plumb Rite, we provide professional boiler fault diagnosis and repair for homeowners throughout the West Midlands.
Our service areas include:
Kingswinford – local boiler repairs, heating faults and hot-water problems
Dudley – boiler fault finding and central heating repairs
Stourbridge – help with unreliable boilers and loss of hot water
Brierley Hill – boiler repairs and heating system diagnostics
Halesowen – professional plumbing and heating support
Whether your combi boiler has stopped producing hot water or your hot-water cylinder isn't heating properly, identifying the correct cause is the first step towards restoring your supply.
Why Choose Plumb Rite?
Plumb Rite is a family-run plumbing and heating business based in Kingswinford, with over 35 years of experience.
Homeowners choose us for:
Gas Safe registered engineers for gas boiler work
Over 35 years of plumbing and heating experience
Local knowledge of Kingswinford and surrounding areas
Boiler repairs, servicing and installations
Straightforward advice on repair and replacement options
Professional fault diagnosis rather than guesswork
Our aim is to identify what's causing the problem and explain the appropriate next steps.
Frequently Asked Questions About Heating Working but No Hot Water
Why is my heating working but I have no hot water?
If your heating works but your taps are cold, the fault may involve the hot-water side of your system. On a combi boiler, possible causes include a diverter valve, flow sensor or heat exchanger problem. On systems with a hot-water cylinder, the cause may involve controls, thermostats or motorised valves.
Why is my combi boiler heating radiators but not water?
A combi boiler may continue heating radiators even when a component involved in producing domestic hot water fails. A diverter valve or hot-water demand sensor fault is one possibility, but professional testing is needed to confirm the cause.
Can a faulty diverter valve cause no hot water?
Yes. On combi boilers that use a diverter valve, a faulty or stuck valve can prevent the boiler from directing heat correctly towards domestic hot water. The valve should be checked by a qualified heating engineer.
Why is my shower cold but my kitchen tap has hot water?
If other hot taps work normally, the problem may involve your shower mixer, thermostatic cartridge or local plumbing rather than the boiler itself.
Can low boiler pressure cause no hot water?
Low pressure can cause some boilers to shut down or operate incorrectly, but it isn't the only possible cause. If your central heating still works, the engineer will need to consider the complete set of symptoms.
Why does my hot water go hot and cold?
Fluctuating hot-water temperature may be caused by changes in flow, a sensor fault, restricted heat transfer or another boiler or plumbing issue. If the problem continues, arrange a professional diagnosis.
Do I need a new boiler if the heating works but the hot water doesn't?
Not automatically. Many hot-water faults can be repaired. Replacement should be considered based on the boiler's condition, age, repair cost and reliability.
Can I fix the problem myself?
You can check accessible settings, fault codes, water flow and boiler pressure in line with the manufacturer's instructions. Do not remove the casing or attempt repairs to internal boiler, gas or electrical components.
Who can fix a boiler with no hot water in Kingswinford?
Plumb Rite provides boiler fault diagnosis and repairs in Kingswinford and surrounding areas, including Dudley, Stourbridge, Brierley Hill and Halesowen. Contact our team to discuss the symptoms and arrange the appropriate assistance.
No Hot Water but Your Heating Still Works? Contact Plumb Rite
If your radiators are warm but your taps are cold, don't assume your boiler needs replacing. The problem may be caused by a repairable fault, but the correct diagnosis matters.
At Plumb Rite, our experienced, Gas Safe registered heating engineers help homeowners across Kingswinford, Dudley, Stourbridge, Brierley Hill, Halesowen and surrounding areas identify and resolve boiler and hot-water problems.
Need help with a boiler that's not producing hot water?
Or call us 01384 293044 to discuss your problem.
Author: Plumb Rite, a family-run business based in Kingswinford, West Midlands.
With over 35 years of experience in plumbing, boiler installation, servicing and heating repairs, Plumb Rite helps local homeowners understand common heating problems and make informed decisions about maintaining their systems.
Our gas boiler work is undertaken by Gas Safe registered engineers.
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