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If your radiators are heating normally but you have no hot water from your taps or shower, your boiler is still operating, but there may be a problem with the hot water side of your system.
Common causes include incorrect boiler settings, a faulty diverter valve, problems with the hot water controls, or, depending on your heating system, an issue with the hot water cylinder.
There are a few simple checks you can safely make yourself before calling a heating engineer.
Why do I have heating but no hot water?
The cause will depend partly on the type of boiler and heating system in your home.
1. Check your boiler settings
Start with the simplest possibility.
Check that your boiler’s hot water function is switched on and that the settings haven’t accidentally been changed.
If you have a programmer or timer controlling your hot water, make sure it’s set correctly.
2. Check for a boiler fault code
Your boiler may display a fault or error code if it detects a problem.
Make a note of the code and check your boiler manufacturer’s instructions to find out what it means.
Some faults may have simple manufacturer-approved troubleshooting steps, while others require a Gas Safe-registered engineer.
3. Check your boiler pressure
Low boiler pressure can affect how some heating systems operate.
Many sealed systems operate at around 1 to 1.5 bar when cold, although this varies between boilers.
Check your manufacturer’s instructions for the recommended pressure for your particular model.
If the pressure repeatedly drops after being restored, there may be a leak or another underlying fault.
4. There may be a problem with the diverter valve
If you have a combi boiler, a diverter valve directs heated water either towards your radiators or your hot water outlets when required.
If it becomes stuck or develops a fault, your radiators may continue working while your taps remain cold or lukewarm.
A faulty diverter valve isn’t something you should attempt to repair yourself. It needs a professional diagnosis.
5. There may be a problem with the hot water sensor
Your boiler relies on sensors to detect when hot water is required and control its temperature.
A faulty sensor could prevent the boiler from producing hot water correctly, even though the central heating continues to work.
6. Your hot water controls may be the problem
If you have a system or regular boiler with a hot water cylinder, check the hot water timer and controls.
If they’re set correctly but the cylinder isn’t heating, there may be a problem with a valve, thermostat, or another part of the system.
7. Is the problem only affecting one tap or shower?
If every hot water outlet is cold, the problem is more likely to involve your boiler or hot water system.
However, if your kitchen tap provides hot water but your shower doesn’t, for example, the problem may be with the individual shower, tap, or plumbing rather than the boiler.
This distinction can help determine whether you need a heating engineer or plumber.
What can I check myself?
Before arranging a repair, you can safely check:
- Whether the boiler has power
- Whether hot water is switched on
- The boiler pressure
- Your timer or programmer settings
- Whether there’s a fault code on the boiler
- Whether all hot water taps are affected
- Whether your heating is definitely operating normally
If the manufacturer recommends resetting the boiler for the fault you’re experiencing, you can follow the instructions in the manual.
Avoid repeatedly resetting a boiler that continues to display the same fault.
Can I fix having no hot water myself?
Sometimes the cause can be straightforward. For example, you may discover that your hot water schedule has accidentally been switched off or changed.
Correcting the timer or control settings may restore your hot water without needing an engineer.
However, don’t remove the boiler casing or attempt to repair valves, sensors, or other internal components yourself.
Gas boiler repairs should be carried out by a Gas Safe-registered engineer.
When should I call a heating engineer?
Arrange professional help if:
- You have heating, but consistently no hot water
- The hot water is only lukewarm
- The boiler displays a recurring fault code
- The boiler repeatedly shuts down
- Boiler pressure keeps falling
- You suspect a diverter valve problem
- There’s a leak from the boiler or heating system
- You’ve checked the controls and can’t identify the cause
An engineer can diagnose whether the problem is within the boiler, hot water controls, or another part of your heating system.
Frequently Asked Questions
Why are my radiators hot but my taps are cold?
If your central heating works but all your hot taps remain cold, there may be a problem with the hot water side of your heating system. On a combi boiler, a faulty diverter valve is one possible cause.
Can a boiler work for heating but not hot water?
Yes. Depending on the fault and boiler type, your central heating can continue working even when there’s a problem producing or delivering hot water.
Should I reset my boiler if I have no hot water?
Check your manufacturer’s instructions. If they recommend a reset for the fault you’re experiencing, you can normally try it once. If the problem returns, arrange professional assistance rather than repeatedly resetting the boiler.
Why is my hot water only lukewarm?
Possible causes include boiler settings, a faulty sensor, diverter valve problems, or another issue with the hot water system. If the problem affects every hot water outlet and continues, it should be investigated.
Do I need a plumber or heating engineer if I have no hot water?
If the problem appears to involve your boiler or central heating system, you’ll usually need a heating engineer. If only one tap or shower is affected while other hot water outlets work normally, you may need a plumber instead.
Need help getting your hot water back?
Having heating but no hot water usually means part of your system is working, but there’s a fault preventing hot water from reaching your taps or shower.
Our network of Gas Safe-registered heating engineers are available across London to diagnose boiler and hot water faults and carry out the necessary repairs.
For urgent boiler and heating problems, assistance is available 24 hours a day, 7 days a week.
Contact Pimlico Plumbers if you’ve lost your hot water and need help identifying and repairing the problem.
Summary
If you have heating but no hot water, start by checking your boiler settings, hot water controls, boiler pressure, and any fault code displayed.
You should also check whether the problem affects every hot water outlet. If only one tap or shower is affected, the fault may be with that individual fixture rather than your boiler.
If all your hot water has stopped working despite the heating operating normally, there could be a problem with a diverter valve, sensor, hot water controls, or another component.
Don’t attempt to repair internal boiler components yourself. If the basic checks don’t resolve the problem, arrange for a Gas Safe-registered engineer to investigate.
