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1st Class Service

Serving Greater London

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No Hot Water?
Here’s What To Check Around Your Home

VHL’s Troubleshooting Guide On Why You Have No Hot Water 

If you’ve found yourself with no hot water there’s no need to panic. Before you call out an engineer, check our troubleshooting guide to see if you can identify the cause of your hot water not working and see if there’s a quick fix. If you still don’t have any luck, then get in touch and we’ll send an engineer to get your hot water back up and running in no time. Give us a call 020 8102 9898 or Booking Online

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What could be causing your no hot water troubles will depend on which type of boiler you have and what the exact problem is. For example, you might have no hot water or heating, intermittent hot water, or your heating is working but there’s no hot water.

Depending on your circumstances, we’ve broken down this guide into different sections starting with 7 of the most common reasons that your hot water isn’t working and then further subsequent sections depending on if you have a gas, electric, closed or open/sealed system boiler, or a combi boiler.

Navigate To The Best Section For You:

Table of Contents

First Things To Check: Most Common Reasons For No Hot Water

1. Check The Gas, Electric And Water Supplies

Whether you have a gas boiler or an electric boiler, checking that your energy supply is connected correctly and in working order should be your first priority. It may seem like common sense, but you also need to check that your water supply is still on as well. 

They are all surprisingly easy to accidentally switch off, or there could be a temporary suspension in your water supply that means no water is coming from your hot tap. If this is the case then you can easily switch the supply back on or query any service disruptions with your supplier. It’s a simple fix but will save you a lot of time and hassle compared to calling out an engineer. 

2. Have You Tried Turning It Off And Back On Again?

Like with a lot of things, sometimes turning your boiler on and off can give it the boost it needs to get your hot water up and running again. In most cases, you’ll find a customer-operated reset button on the front of your boiler and you can simply refer to your boiler’s manual to initiate a reset. 

So, locate your reset button and try resetting it according to the manufacturer’s instructions. If you can’t find the button or know that it is concealed in the unit then you’ll need a qualified professional to access it for you so it’s best to get in touch with us! If resetting it doesn’t work, try switching the boiler off at the mains for a few seconds, before turning it back on again. 

3. Check The Thermostat Settings

If your thermostat is playing up or has been accidentally knocked to the wrong setting then you could find that either you have no hot water at all or your hot water isn’t getting hot enough. If your temperature is set below 21℃ your boiler might not come on at all, so you’ll need to increase it. 

Most modern boilers allow you to easily change the temperature of your radiators or hot water with a simple user-accessible dial. It may help to kick-start your boiler if you turn these up to high for a short period of time and then reset them to the normal temperature once the hot water has returned. Again, if this doesn’t work then you’ll need to get an engineer to do the rest. 

Plumber Checking Thermostat Settings

4. Make Sure The Clock And Timer Is Set To The Right Time

If you use the timer on your boiler, make sure that the clock is set to the right time, as the boiler is often forgotten when the clocks go forward or back. You should also make sure that the timer is set for the hot water to come on at the right time. If you are using the timer but have not correctly set it, then your heating will not come on when you want it to, which can cause you to have no heating or hot water. If you’re unsure about how to reset the timer on your system, check your boiler manual. 

5. Is The Pilot Light On?

If you have a gas boiler check in the pilot light has gone out. If so, try relighting it following your manufacturer’s instructions. If it keeps blowing out, it’ll need to be checked by an engineer. And if you smell or suspect gas, don’t attempt to reignite the boiler. 

6. Is It A Water Pressure Issue?

Low pressure may be the reason for your lack of hot water. For your boiler to work at its best, your ideal water pressure should be between 1 and 1.5 bar, which is usually displayed on a gauge known as a ‘Manometer’, usually located where the water supply pipes are connected to the boiler. 

So, if the pressure’s not quite high enough, adjust it carefully using the filling loop. Only attempt to re-pressurise the boiler if your manual indicates that it is safe to do so and you are comfortable performing this task yourself.

7. Has There Been A Recent Power Cut?

If there has been a power cut recently, your boiler may have reverted to factory settings once the power was restored, so it may not be functioning as it used to. Check all of these settings and alter them as necessary – a simple but quick fix! To remedy this, you simply need to change the boiler’s settings so that it’s back to the way it was before the power cut.

8. Do You Have A Water Tank Or Cylinder?

If so the problem might lie with the thermostat/programmer on the tank or cylinder itself. Have a look to make sure it’s displaying the right settings and change them if you need to. You’ll know if there are any issues with your hot water supply if the water tank or boiler is showing some kind of error code on the front panel display. 

Each code corresponds with a different boiler fault, so it is important to check the code against the manual for more information. For help and advice on any faults with your boiler or water tank get in touch with our team by calling 020 3918 6405

9. See If Your Pipes Are Frozen

Another cause of no hot water could be frozen pipes, particularly in long periods of cold weather. The most likely pipe to freeze is the condensate pipe, which is the waste pipe carrying condensation from the boiler to the drain outside

To remedy this, try pouring hot – but not boiling – water over the pipe. If you attempt to fire up your boiler and it still doesn’t work, try unfreezing them again. If this still doesn’t work, it’s time to give us a call on 020 8102 9898 or by Booking Online

10. Check For Leaks

This issue is related more to the pressure levels of your boiler, but can still have an effect on the availability of hot water. If your central heating system does have a leak somewhere, it will result in a drop in pressure, making it difficult to get any hot water out of your taps. Have a look around your property and see if you can find any signs of wet patches around ceilings, pipes and woodwork as well as mould building up.

11. If There’s No Hot Water And No Heating You Could Have An Airlock

If you have no hot water and no heating then the most likely culprit is an airlock. As the name suggests, this is when air becomes trapped in water pipes, being less dense than water, it can collect in high points on the pipes leading to partial or complete water blockages.

One popular method to fix this is to attach a hosepipe to a working tap e.g. your cold water tap, and then connect it to your hot tap. Turn the broken tap on first, fully open, and then turn on the working tag all the way up. The higher water mains pressure of the cold tap should force the airlock out – leave the taps running for a few minutes to make sure. If this doesn’t resolve the issue there could be a need to drain the system down, in which case, it would be a good idea to call an engineer on 020 8102 9898 or by Booking Online

12. Is Your Boiler Due A Service?

The best way to avoid a nasty surprise with your hot water supply is to ensure your heating and hot water system is regularly maintained by a qualified professional to help keep everything running safely and smoothly all year round. 

Boiler Specific Troubleshooting:


If you’ve tried all of the above but you still have no hot water or intermittent hot water then it’s time to look at some boiler-specific troubleshooting.

Sealed System Boiler Or Combi Boiler Checks

No Hot Water When Heating Is On? The Diverter Valve Could Be The Problem

If your central heating system is functioning perfectly but there is no hot water coming from your shower or taps, it is likely an issue with the diverter valve. Similarly, if you have a combi boiler and your central heating is not working but your hot water is working then it could be the same root problem.

The diverter valve allows a combi boiler to switch between heating your radiators and your hot water, so when you turn on your hot tap, the diverter valve opens and sends hot water to the tap. 

Unfortunately, if this isn’t working as it should be you won’t be able to remedy a diverter valve problem yourself so you’ll need to call out an engineer to help you by 020 8102 9898 or by Booking Online

Make Sure That You Don’t Have Low Water Pressure

If you have a combi boiler then low water pressure could be the cause of your no hot water problem. The water pressure of your boiler should be set to around ‘1 bar’ which you should be able to see on the pressure gauge of your boiler – refer to your boiler manual if you’re unsure what this is. 

Typically there is an indicator needle showing the pressure that the boiler was set to when it was installed, so compare it against this. If the water pressure is too low, you may be able to re-pressurise it yourself by carefully using the filling loop and following the instructions in your boiler’s manual. If these instructions require you to remove your boiler panel, then you should call an engineer instead.

It is worth noting that pressure drops can be caused by water leaks, so if your water pressure is too low, you should also check for leaks which you can read about in the gas boiler section of this page.

Gas Boiler Check

There are several potential reasons why your gas boiler may not be functioning properly. You must always use caution where gas appliances are involved should you choose to tackle a problem yourself, as a gas leak poses a serious safety risk and can cause a fire or explosion. If you are in any doubt, give us a call on 020 3918 6405 and we can send out a professional to help. 

Has Your Pilot Light Gone Out?

The most common cause of no hot water from your gas boiler is the pilot light going out. The pilot light is used to ignite the gas which heats the water in the boiler.

If the pilot light has gone out, it is essential that you carefully follow the instructions for your boiler model to make sure that you are relighting it safely. Older gas boilers may require a match to light them, while newer styles use an ignitor. If you have any uncertainty then get in touch with a professional as gas boilers are hazardous if you aren’t confident about what you’re doing. 

However, if your pilot light won’t stay lit then it is likely a problem with the thermocouple, which senses when the pilot light is lit and opens a gas valve to keep it lit. This is a safety device to ensure that gas does not leak out when the pilot light is not there to burn it. If the thermocouple needs replacing, it is best to call an engineer.

Is The Pressure Relief Valve Faulty?

The pressure relief valve regulates the pressure in your tank and relieves excess pressure to prevent your boiler from exploding. When this valve fails, however, rather than causing the pressure to build up, it actually causes it to drop, as it relieves pressure before it gets to a dangerous level. If the pressure relief valve is faulty, it will need to be replaced.

If you are confident that you can replace it yourself, this will involve part draining the tank before removing the old valve and replacing it with a new one. You may prefer to get an engineer to do this for you.

Check For Leaks – Another Cause Of Low Water Pressure

You’ll know that your central heating is leaking because there will be a drop in pressure, along with a loss of water. In addition to your no hot water problem, this could also lead to rot and structural problems if left untreated, so it is worth checking to be sure.

When you check your hot water tank for leaks, be aware that the water in it will be very hot. The drain valve at the bottom of the tank is probably the first place to check. If this is dripping, try unscrewing it a little using a screwdriver to release any sediment which may be causing it to fit loosely, and then retighten it all the way to stop the drip. 

Keep in mind while checking for leaks that condensation on the boiler is often mistaken for a leak. As a general rule, if the tank is hot and there are drips then there could be a leak. 

If there is a small drip coming from the spigot, you may be able to cap this. If it is leaking a lot, or the leak is coming from where the valve connects to the tank, then you will have to replace the valve. This can be a difficult job and it would be best to get an engineer to do this.

If you are experiencing a leak from the tank itself then the whole tank will have to be replaced and you should call an engineer. You may be tempted to just put up with a small leak, but there is no way to know if or when the tank may just give out and leave you with a lot of mess and hassle.

Check Other Gas Appliances Are Functioning Properly

If you have other gas appliances in the home, check that these are functioning correctly. If they are not working correctly either then it is likely a problem with your gas supply rather than the boiler and you should call an engineer.

Electric Boiler Check

Electric boilers and hot water heaters are generally rather reliable, but when something does go wrong you will usually require an engineer, as the high voltage electricity which supplies it poses a significant risk. If you are intending to work on the boiler yourself, you must make sure that the power is off and only do so if you are confident.

Troubleshooting electric boilers can be a complex matter, as you often need particular testing tools to get to the root of the problem. We encourage you to get in touch with us by calling 020 8102 9898 or by Booking Online and we’ll send an engineer to help you if you suspect any of the following problems. 

Has The Circuit Breaker Tripped?

The first thing to do is to check your main fuse box to see if the circuit breaker has tripped for any reason, or if a fuse has blown. If this is the case, you should be able to simply reset the circuit breaker or replace the fuse. If this does not work, or your boiler trips the circuit breaker again once it has been reset, then you may be experiencing an electrical fault and should call an engineer or electrician to repair it.

Is There A Problem With The Heating Elements?

Most electric water heaters have two heating elements; one at the top and one at the bottom, along with a thermostat for each element. Generally speaking, the upper element controls the lower one, so if the upper element or thermostat stops working, you will have no hot water at all. If the lower one stops working, you may find your hot water not getting hot enough.

To check the heating elements, you will need to use an element tester and a voltage tester to check the current to the elements and whether they are grounded. You will need to do this for both elements, regardless of which one you suspect might be faulty.

If you do not have these testing tools or are not confident about working with electricity then you should call an engineer. If you do choose to check them yourself, you must make sure that the power to the boiler is off before you begin.

Is There An Issue With Your Thermostat?

The internal thermostat could be the cause if you don’t have enough hot water. For safety purposes, unlike the thermostat that you can sometimes find on your boiler, this thermostat is not easily accessible and its factory settings are usually the safest option to use. Setting the temperature too high can leave you with water which causes severe burns in moments, so it is important that you do not set your thermostat to dangerous temperatures.

If you suspect that there is a problem with your thermostat, you should call an engineer. If you do decide to adjust it yourself, you must make sure that the power is switched off before you start.

Open Vented System Boiler Check

Is The Ball Valve Float Stuck?

If you have an open vented system boiler that has an additional water tank, which is usually stored in the loft, then it is possible that the ball valve float has become stuck, preventing water from circulating around the system.

If you are able to safely access the water tank, then it may be a good idea to check the ball float valve. If there isn’t much water or no water at all in the cistern, then this is a sign that the ball float valve is stuck. Gently move the ball float valve arm to free it, but be careful not to force it. This should allow the water to flow freely.

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Get In Touch With VHL For Help With All Boiler Repairs & Servicing

Here at VHL, our central heating services include all aspects of boiler repair, replacement and maintenance. At VHL, we have over 24 years of experience providing the best quality products and services to customers throughout London, and southeast England.

If you find yourself with no hot water or with no heat coming from your radiators, then you might be in need of a new boiler. Our Gas Safe engineers and installers will replace your old boiler with a new, high-quality boiler to meet your needs.

If you find yourself with a lack of hot water and you are unable to find a DIY remedy, our team of plumbers and Gas Safe Engineers are standing by to help get your hot water supply flowing again. Simply give us a call on 020 8102 9898 or by Booking Online

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No Hot Water Frequently Asked Questions

There are several reasons why you might not have hot water, ranging from common problems, such as a problem with your water or power supply, boiler settings, thermostat, timer, recent power cut to more complex issues, such as boiler pressure, a potential airlock or frozen pipes. VHL’s Troubleshooting Guide shows you how to identify and remedy these problems without needing an engineer in most cases.

This is likely an issue with your diverter valve and you’ll require an engineer to help you with this one. The diverter valve allows a combi boiler to switch between heating your radiators and your hot water, so when you turn on your hot tap, the diverter valve opens and sends hot water to the tap.

If you only have hot water when your central heating is on its maximum setting then this is a likely indicator that your diverter valve is experiencing a fault. For this problem, you’ll have to call out an engineer to help you as you won’t be able to remedy it yourself.

The water pressure of your boiler should be set to around ‘1 bar’ which you should be able to see on the pressure gauge of your boiler – refer to your boiler manual if you’re unsure what this is. If you have no or very low pressure that doesn’t stay at the correct level even after you adjust it then this is a likely indicator that there’s a bigger issue and could be the result of a leak. This can lead to further damage beyond your no hot water problem so you should get in touch with us so an engineer can come and take a look.