It is often said that you don’t know what you’ve got until it’s gone. This is certainly the case with your home’s hot water, which we often take for granted while it is in perfect working order, but will complain about tirelessly when it’s playing up.
If you find yourself without hot water in your taps or shower, you’ll want to get things up and running as soon as possible, so take a look at our troubleshooting guide to find out when there’s a quick fix and when you’ll need to call an engineer. VHL offers domestic services for houses and apartments, or commercial services for work & office, schools and business premises.
This guide is split into three sections to give you the most relevant information for your boiler type. Navigate to:
First things to check
- Check the gas, electric and water supplies
- Reset the boiler
- Clock and timer
- Power cut
- Diverter valve
- Airlocks in pipes
- Frozen pipes
- Low pressure - sealed system or combi boilers
- Stuck ball valve float - open vented boilers
Gas Boiler checks
Electric Boiler checks
First Things To Check: General Tips
Check the gas, electric and water supplies
Whether you have a gas or electric boiler, you should make sure that the energy supply is connected and in working order. You should also make sure that the water supply is still on. These are all surprisingly easy to switch off accidentally and can save you the hassle of calling out an engineer unnecessarily.
Reset the boiler
If your boiler has a customer-operated reset switch (not one that you need to remove the casing to access) then try using this to reset the boiler. You could also switch off the power to the boiler and switch it back on again. This may remedy the problem.
Modern boilers allow you to easily change the temperature of your radiators or hot water with a simple dial. Check that these have not accidentally been knocked to the coldest settings. 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.
Clock and timer
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.
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.
If your central heating is functioning perfectly but there is no hot water coming from your shower or taps, it is likely an issue with the diverter valve. This 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 are experiencing this problem then the diverter valve may be faulty, or it may be stuck in the central heating position.
Airlocks in pipes
If there is no water from the hot tap, or the hot water supply is spluttering, 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.
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, call an engineer.
Low pressure - sealed system or combi boilers
Low pressure can be a cause of many heating niggles if you have a sealed system or combi boiler. This is the type of boiler which does not have an additional tank in the loft.
If your hot water pressure is low all of a sudden, check the pressure gauge on your boiler, which should be set at around 1 bar. There may be an indicator needle showing the pressure that the boiler was set to when it was installed, so compare it against this.
If the pressure is too low, you may be able to re-pressurise it yourself by 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. You can find out more about checking for leaks here.
Stuck ball valve float - open vented boilers
If you have an open vented system boiler, that is, a boiler with an additional water tank, usually situated in the loft, then the ball valve float could be stuck, preventing water from circulating around the system.
If you are able to safely access the tank, check the ball float valve. If there is no or not much water in the cistern, it is likely a sign that it 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.
Gas Boiler checks
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, call an engineer.
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, you must make sure to 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 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 probably best to call an engineer.
Pressure relief valve
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
If your central heating is leaking, this will lead to a drop in pressure, along with a loss of water. Besides the problems with your hot water, this may also lead to rot and structural problems if left untreated, so it is worth checking to be sure.
It should be noted while checking for leaks that condensation on the boiler is often mistaken for a leak. If your boiler is used quite a lot and there is a lot of cold water going into the tank then you may get a lot of condensation. This will dry up once the boiler heats up. If your water tank is cold and there are drips then it might just be condensation. If the tank is hot and there are drips then there could be a leak.
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.
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 any other gas appliances
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.
If you often find that you don’t have enough hot water, it may be the case that your water tank is too small for the amount you are using it. If you have a lot of people in the house or you consider your hot water usage to be high, it might be worth getting in touch with an engineer to discuss whether you need a larger tank to ensure that you don’t run out of hot water when you need it.
Electric Boiler checks
Electric boilers 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.
The first thing to do is to check the circuit breaker to see if it 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.
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 have some hot water, but not 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.
The thermostat could be the cause if you don’t have enough hot water. For safety purposes, the 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.
Here at VHL, our central heating services include all aspects of boiler repair, replacement and maintenance. If you haven’t got any hot water and you are unable to remedy it yourself, we will be more than happy to help. Simply give us a call or get in touch online.