No Hot Water: Common Causes & How To Fix It

James Elston
Written by James Elston
Updated on 18th April 2024
Posted on 11th February 2024
No Hot Water from Your Boiler - Common Causes & How to Fix it

Why Do I Have No Hot Water? Causes & fixes

boiler no hot water

If you’re experiencing the frustration of having no hot water coming from your gas boiler, you’re not alone. It’s a common issue that can disrupt your daily routine, especially during the colder months.

However, before you panic and call out a heating engineer, there are several troubleshooting steps you can take to identify and potentially resolve the problem yourself.

In this article, we’ll guide you through the process of diagnosing and fixing the issue of no hot water from your gas boiler and whether its better to replace your boiler or repair it.

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Common causes of a boiler with no hot water

When you find yourself with no hot water from your combi boiler, it can be a frustrating experience.

However, understanding the common causes can help you troubleshoot the problem more effectively. Here’s an overview of the typical issues and some solutions:

low pressure boiler

Low Boiler Pressure

The pressure in your boiler should be within a specific range for optimal operation. If the pressure is too low or too high, it can affect the boiler’s ability to produce hot water.

Checking the pressure gauge and adjusting the pressure as needed can often mean that you can resolve low pressure in your boiler yourself.

Diverter Valve Failure

The diverter valve in your boiler plays a critical role in directing hot water to your taps or radiators. A failure in this valve can result in a lack of hot water. This issue often requires the expertise of a Gas Safe engineer for the repair of the faulty diverter valve or a replacement.

Faulty Thermostat

fix no hot water boiler

A malfunctioning thermostat can fail to signal the boiler to heat water. Ensuring that the thermostat is set correctly and in good working condition is essential. In some cases, recalibrating or replacing the thermostat may be necessary.

A faulty central heating thermostat will usually require a replacement.

Frozen Pipes

During cold months, pipes can freeze, causing blockages that affect the boiler’s operation. Frozen condensate pipes are the most common cause of not hot water in freezing temperatures.

Gently warming the affected pipe can thaw the ice and restore function. Restarting the boiler might be needed after addressing the frozen pipes

Blocked Hoses or Heat Exchanger

Over time, dirt and debris can accumulate in the boiler’s hoses heat exchangers can cause major problems and replacing these parts or cleaning them out can restore your hot water quickly. Things like magnetic filters and a chemical flush every 5 years can stop this issue.

Pilot Light or Ignition Problems

gas safe logo

For boilers that use a pilot light or ignition system, issues with these components can prevent the boiler from heating water. Ensuring that the pilot light is lit or the ignition system is working correctly is vital.


Air trapped in the system can prevent water flow to the boiler. Bleeding the radiators to release trapped air might resolve this issue. A boiler airlock would have to be diagnosed by a Gas Safe registered boiler engineer.

Gas or Electricity Supply Issues

Problems with your gas or electricity supply can interrupt the energy needed for the boiler to operate. Checking other appliances will usually quickly tell you if the gas supply or electricity supply is the issue.

Our Expert Gas Safe Engineer Says:

When you're getting no hot water from your boiler, it can be frustrating, but often things can be fixed without calling a Gas Safe engineer such as myself. Many times, I have attended to an issue with no hot water, but it has been something as simple as frozen condensate or low boiler pressure. never attempt to fix inside the boiler yourself!

James Murfin

Gas Safe Registered Heating Engineer

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How to fix no hot water from your combi boiler and the main causes of this problem

No hot water from a combi boiler quickest fix (hopefully):

Low Water Pressure

If your combi boiler is not heating water or firing up for hot water this may be due to the boiler pressure being too high or too low.

This can result in your combi boiler working but not producing hot water when required. If you don’t have any hot water, and you haven’t yet identified a cause, check the pressure gauge on your boiler.

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This may solve all your heating and hot water problems right away.

However, if it keeps happening, we have also listed other potential causes when you will likely need a Gas Safe registered heating engineer, a new boiler or boiler cover here if your boiler is starting to break down.

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Want to extend the life of your boiler? Book a boiler service online now to ensure your boiler is in tip top condition and lower the chances of a costly breakdown.

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Video: No Hot Water From Combi Boiler?

There are a few possible reasons why there’s no hot water coming from your combi boiler, find out more now.

Combi boiler no hot water but central heating works?

tools to fix no hot water from boiler

Is there anything more distressing than turning on the taps to find that hot water has abandoned you in your hour of need, especially if you have no hot water from boiler but the central heating works.

This is likely due to a faulty diverter valve not changing from hot water to central heating properly which we explain below.

When it’s freezing outside, or you’ve endured a day from hell, a cold shower is probably up there with the last things you need. But there’s no major need to panic.

If there’s no hot water coming from your boiler, there are a number of reasons and easy fixes you need to consider.

Why is there no hot water coming from your boiler but heating works? 

worcester 4000

If your boiler is firing up, but there is no hot water but heating works, then you have come to the right guide on why this could be.

Despite the wonders of modern technology, there is a risk of things going awry with your boiler, and a sudden refusal to heat water can be a very worrying turn of events.

The good news is that, often, there’s a simple solution.

If you’re seeking solace while shivering after a particularly unpleasant lukewarm kettle bath, you’ve come to the right place! Here’s a handy guide to why your gas combi boiler is not heating water. 

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Common reasons why the heating works but no hot water from your boiler

Even the most optimistic, cheery types may struggle to stay positive when the boiler is playing up, and the heating works but there’s no hot water running freely from the bath taps. If you’re having issues with your gas boiler, and you haven’t got any hot water, there could be several reasons.

We’ll talk you through some of the most common obstacles now so that you can hone your gas boiler with no hot water fixing and troubleshooting skills to see if you can find a solution and save yourself from buying a new boiler.

Before you begin your quest to fix a broken boiler

Before you start frantically trying to decipher error codes or check individual components of the heating system, it’s a good idea to make sure that your home hasn’t been affected by any kind of outage that might impact the boiler.

If there’s been an incident in the local area, or a power cut, for example, the provision of services might be interrupted.

Check other appliances and your gas supply and look on the Internet for news and updates. If there is a local or regional issue, your boiler should return to normal as soon as it has been fixed.

If there aren’t any issues to report, and your boiler is flying solo in terms of not playing ball, these issues might be to blame:

No hot water from boiler causes & how to fix it

Pilot light problems

no hot water from boiler

This may sound like a catchy 21st-century hashtag, but it’s actually a very common cause of combi boilers going on the blink when you fancy a hot shower.

The pilot light must be illuminated for the boiler to function, so if your light has gone out, this is probably the root of your boiler dilemmas.

To generate hot water, boilers burn gas or oil, and to do this; they need the pilot light to be on. If the pilot light has gone off, this means that your boiler will not produce hot water.

If you have an old boiler, you might be able to spot the pilot light through the frame of the unit. In this case, it may be possible to see if the light has gone off.

In the case of newer boilers, you’ll usually be presented with an error code, which pops up on the monitor.

While this is probably not the best ‘you’ve got mail’ moment you’ve ever enjoyed, at least you’ll be able to tell what the problem is, even if there’s an energy crisis you don’t need to devote more time and energy to other possible causes. 

If the pilot light has gone out, or you’ve opened the boiler cupboard to find an error code of doom, the next step is to grab your boiler manual and follow the instructions to fire up the pilot light again.

There should be clear guidance provided, and hopefully, once you’ve followed the steps, the boiler should respond.

If you don’t get the reaction you desired, and you still haven’t got a functioning pilot light, it may be time to call in the pros. In many cases, it will be possible to carry out repairs, and your engineer will discuss their findings with you.

If you have an old boiler, see the latest boiler costs and prices to upgrade to a more reliable boiler.  

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Frozen pipes

no hot water from boiler

If you’re not willing to channel Elsa and Anna and let it go, you’ll want to find a quick fix for frozen pipes.

This is a problem that you’ll probably have guessed occurs in the winter months when temperatures take a tumble, and the ground is covered in frost and ice. If it is cold outside, there is a risk of the condensate pipe freezing.

This pipe runs from the boiler to the outside of your home. If the duct freezes, this will cause the boiler to shut down completely due to safety reasons.

The result: cold showers all-round. Fortunately for those keen to rectify the problem, there is a simple fix.

The key is to try and gradually warm up the affected pipe by placing a cloth over it or running warm water over the duct. This will help to melt the ice and, hopefully, bring your boiler back to life. It is important to note that you’ll need to restart the boiler if the pipe has frozen. 

Read our guide if your shower is cold but taps are hot here for more information too.

Check for diverter valve failure

no hot water from boiler

Deep within the intricate workings of your combi boiler lies an essential cog known as the diverter valve. This component is the lollipop lady of the system, and it is responsible for directing the flow of water to reach the relevant appliances.

If there is a fault, and the diverter valve fails, this will result in a lack of hot water. The radiators won’t respond when you turn your heating on, and you won’t have any hot water to wash up or take a shower.

In most cases, this problem will require the expertise of an engineer. If the valve has failed, a new one will be installed, and you should have hot water again in no time.

If the boiler is old, and other problems are likely to cost you money in the foreseeable future, your engineer may advise you to consider replacing a boiler rather than paying out for ongoing repairs.

Newer units are more powerful and they’re also much more efficient, which will save you money on your energy bills. 

Learn more: How to balance radiators for efficiency

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Boiler low pressure

pressure gauge

If you take a moment to look at your boiler, you’ll notice a pressure gauge. The pressure should be in the green zone. If the boiler pressure is too high or too low, this can result in your combi boiler working but no hot water will be coming from the boiler.

If you don’t have any hot water, and you haven’t yet identified a cause, check the pressure.

If the gauge is in the red zone, either above or below the optimum level, you should be able to fix the problem by following the instructions in the boiler manual. If you need to increase the pressure, the handbook will tell you how to top your boiler up.

You should notice the gauge move, and hopefully, once the pressure is right, you should have hot water again.

If the pressure is too high, the best place to start is bleeding your radiators. This should release pressure. If this doesn’t work, it may be possible that your boiler has a broken part, and you’ll need to consult an engineer.

Boiler leaks can also cause low boiler pressure. If the problem is a leak, rather than a gradual loss of pressure, an engineer will be required. 

Faulty thermostats

If you’ve got hot water, but it’s lukewarm rather than hot enough to enjoy a shower, or the water is only hot enough when the heating is also on, then it is worth checking that there is no problem with the thermistor.

nest smart thermostat

This is a small part, which is relatively cheap to replace by a Gas Safe engineer.

A note about thermostats:

Many people now use thermostats at home as a means of controlling the temperature and saving money on energy bills. It is worth noting that thermostats are linked to heating and radiators, rather than hot water. If you have a problem with your hot water supply, but your central heating is working fine, the thermostat will usually be irrelevant.

In some cases, however, the thermostat can also be used as a timer. If you use your thermostat as a timer as well, a thermostat fault might shut the boiler down completely, meaning you’ll be without both heating and hot water. 

Some boilers also have a thermostat dial, which enables you to adjust the temperature of your radiators and hot water. If you’re struggling to get hot water, check the settings and make sure you haven’t knocked the water dial onto the coolest temperature. 

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Combi Boiler No Hot Water Problems and How To Fix

Nobody wants to be stuck without hot water for any length of time. If you haven’t got any hot water, here’s a plan of action to follow:

Check your utilities


Sometimes, when you have issues with your boiler, it’s not actually the boiler that is faulty or broken. The first thing to do if you encounter problems is to check the utilities and make sure that you’ve got an electricity and gas supply.

If you’ve got a monitor on your boiler, for example, and there’s nothing on your digital screen, this may indicate that you’ve had a power cut.

If this is the case, once the power supply is restored, your boiler should hopefully stage a Lazarus-style recovery, and you should be able to run a hot bath.

Look for error codes or fault codes

question mark

Many modern replacement boilers have displays or screens that indicate what has gone wrong. You might find symbols or specific lights illuminated, which you can decipher using the manufacturer’s manual.

If you don’t have this to hand, Google is always a useful resource, and you should be able to find the information you’re looking for on the brand website. Once you know the cause of the lack of hot water, you can decide whether to attempt DIY repairs or to call an engineer. 

Check out our list of Worcester boiler error codes here if you have a Greenstar boiler.

Inspect the controls

If you’ve carried out the steps above, and there’s still no joy, take a moment to inspect the controls on your boiler. Make sure you haven’t accidentally changed the settings to turn either the hot water or the heating off or adjust the temperature of the water to cold.

In some cases, a timer is used to control hot water, as well as heating. If you have a timer, and you haven’t got hot water, check the timer and ensure you haven’t knocked it or got your timings wrong. Adjusting the clock may solve the problem. 

Seek expert advice

boiler cover (service)

If you’ve explored all the common causes of a boiler not heating water, and you’ve been through the steps listed above, and you still don’t have a clue what has gone wrong, don’t hesitate to seek expert advice.

Gas Safe boiler engineers are trained to carry out rapid troubleshooting, and they use advanced technology and equipment to identify potential hurdles and find solutions. They will find out why your boiler is not working and usually work with the most common boilers and central heating manufacturers.

No Hot Water But Central Heating is Working

The good news is that at least if there are any drastic issues, you will only need to replace your boiler as they central heating system is working perfectly fine, however, ignoring any issues with not hot water from your boiler is a big mistake and even if your hot water starts to work again, it is likely that there will be further issues down the line.

Prevention is better than the cure in this case and you don’t want to be without hot water from your combi boiler in the depths of winter when you need it the most.

Combi boiler not heating water up properly or getting hot

If your combi boiler water is not getting hot, one thing you can do is check that the hot water is turned on or that the flow temperature has not been turned down.

If it has been turned off then you can simply turn the hot water on or make sure that you turn the temperature up on the combi boiler if it has been turned down somehow. More often than not this can be after your annual boiler service or if you have had a recent repair or fix from a Gas Safe registered engineer.

Heating but no hot water from boiler, do I need a new one?

If you’ve reached the end of your tether and you’re convinced that there’s no chance of enjoying a hot shower, you might assume that you need to replace your boiler with taking advantage of such a luxury again.

viessmann vitodens 050-w combi boiler

While in some cases, a new boiler replacement may be the preferred option if you have heating but no hot water, but in the vast majority of cases, there will be a much simpler and cheaper solution.

Many problems can be fixed at home, and even if the issue seems more complex, engineers can often find a remedy. 

New boilers will usually only be recommended for clients who have old boilers, which are likely to need ongoing repairs that are both costly and inconvenient.

If your boiler is more than 15 years old, and it’s prone to wobbles, it may be best to consider investing in a newer, more efficient and cost-effective model.


How can I determine if the issue with no hot water is due to a more complex electrical problem within the home’s wiring, beyond the boiler itself?

To accurately pinpoint the cause of a hot water issue that might be related to intricate electrical problems, it’s important to contact a qualified electrician. This professional will meticulously examine the electrical wiring and connections in your home that link to the boiler, ensuring a thorough evaluation.

What are the long-term effects of repeatedly fixing common boiler issues on the overall lifespan of a boiler?

When you frequently deal with common issues in your boiler, it can lead to faster wear and tear on its parts. This not only shortens the boiler’s lifespan but also increases the risk of encountering more serious problems down the line.

This cycle of repair and wear can ultimately lead to significant breakdowns, requiring more extensive and costly repairs or even premature replacement of the boiler.

Are there specific brands or models of boilers that are known to have fewer issues with hot water supply, making them more reliable choices for consumers?

When it comes to selecting a boiler that is less prone to hot water issues, it’s advisable to delve into consumer feedback and heed the advice of industry experts. Viessmann for example use a stainless steel heat exchanger to reduce the effects of heat expansion.

The reliability of a boiler can significantly differ depending on the specific model, how it’s used, and the regularity and quality of maintenance it receives.

Get Your Hot Water Working With a New Boiler

If you would benefit from a new boiler, your engineer will be able to go through the cost of both repairing your existing boiler and buying a new one. You then have all the information you need before you decide on the best port of call.

It’s worth bearing in mind that buying a new boiler may seem like an expensive option, but the best combi boilers can cut the cost of heating your home significantly. Check out our new boiler deals

If you’re having issues, and you’ve got no hot water from your boiler, don’t suffer and shiver in silence. Help is at hand! Our engineers are on the Gas Safe register and are experienced in all boilers. Whether the issue is a simple water pressure issue or worse, help is readily available.

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Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 11th February 2024

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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