If your heating is on, but you’ve got no hot water, it’s easy to get into a panic.
We take having hot water for granted and it can seem like a nightmare when it suddenly goes off. And that’s understandable – nobody wants a cold bath or shower, especially in the middle of winter!
But although it’s a frustrating and inconvenient problem, it’s not uncommon. And there’s often a simple fix.
So, before calling an engineer, it’s worth making sure that your water woes aren’t down to something as simple as a family member accidentally turning down your thermostat!
To help you get back up and running as soon as possible, we’ve created this handy checklist.
By following the simple checks below, you might be able to get your hot water back without having to call for help.
Checks to make when you have no hot water
If your hot water isn’t working, there are a few simple checks that you can make to isolate the problem and put it right:
1. No hot water: Check your boiler for a fault code
Forgive us for pointing out the obvious, but the first thing to do when your hot water goes off, is to check that your boiler’s working.
Modern combi boilers have displays that show error messages or fault codes when the boiler runs into a problem.
All combi boilers display different fault codes depending on the model. So, you’ll need to check the manual that came with your boiler to find out what the code is telling you and what you need to do to address it.
Some common fault codes which might be displayed if you have no hot water include:
- A low pressure fault;
- No gas, or insufficient gas pressure;
- No ignition;
- Condensate pipe is blocked (frozen)
If your boiler isn’t displaying a code, or the display panel isn’t showing anything at all, that leads us on to our second check…
2. No hot water: Check you still have gas, electricity, and water supply
Some hot water problems are not actually caused by a fault with your boiler. It could be that there is a problem with the supply of your electricity, gas and water.
So it’s a good idea to eliminate any potential problems with your utilities first. This is very simple to do.
To check your electricity supply, you can start by looking at your boiler’s control panel. If it isn’t displaying anything, check whether other appliances in your home are getting any power. Check your fuse box to make sure that a switch hasn’t tripped and cut power to your system.
To check your gas supply, try using another gas appliance, such as the hob on your cooker. If this still works, it isn’t a problem with your gas supply.
To check your water supply, just turn on a tap to check that you’re still getting water.
Once you’ve eliminated problems with your electricity, gas and water supply, you can move on to other checks.
3. No hot water: Check your boiler’s timer
If your boiler’s hot water is controlled by a timer, this may be the cause of your problem.
You might be fooled into thinking you have no hot water at all, when, your timer’s just set to come on at an unexpected time.
Something as simple as the clocks changing, a power cut, or an accidental knock might have altered your timer’s settings without you knowing. So, check that the clock and timer are set to the right time.
Adjusting your timer may be a very simple fix to the dreaded no-hot-water problem.
4. No hot water: Check your thermostat
Similarly, to checking your timer, you should also check your boiler’s thermostat.
The thermostat is a control used to regulate the temperature in your heating system. If this isn’t working, or has been set incorrectly, it could be the cause of your hot water problem.
You might have an analogue mechanical thermostat that operates with a dial, mounted on a wall in your main living area or hall. Or, you may have a more modern digital thermostat that you can also control from your smartphone.
But whichever sort of thermostat you have, you should check that it hasn’t accidentally been switched to ‘Off’.
You can test whether your thermostat is working by setting the temperature to a higher value than normal. Hopefully, you’ll hear the boiler firing up, and you’ve resolved the issue.
But if your thermostat fails to respond, you’ll need to get help from a heating engineer.
5. No hot water: Check the thermostat on your cylinder (if you have one!)
Your cylinder may have a thermostat attached. If there isn’t a thermostat on your cylinder, don’t worry – this just means that the temperature of the water is controlled by your boiler thermostat.
Check your cylinder for a thermostat. If it has one, check that it’s set to the correct temperature and timings. If not, adjusting it might resolve your problem.
6. No hot water: Check whether your boiler needs resetting
Ah – the classic: have you tried switching it off and on again?!
The power cycle doesn’t just work for computers though, it can work for boilers too!
Your boiler is a complex and hard-working appliance that’s working 24/7, and occasionally it will benefit from a reset.
Some boilers have a reset switch that you can operate yourself but be careful to follow the manufacturer’s instructions. If your reset button is inside the boiler’s casing, you’ll need to leave this to a Gas Safe engineer.
Hopefully, resetting your boiler will give it the boost it needs to get your hot water up and running again.
7. No hot water: Check your pilot light
Another reason why you might not be getting any hot water is if there’s no pilot light on the boiler or the boiler pilot light keeps going out.
The pilot light ignites the gas, which heats the water in your boiler. So, if it’s gone out, you’ll need to reset it following your manufacturer’s instructions.
If it keeps blowing out, it’ll need to be checked by an engineer.
8. No hot water: Check your boiler’s pressure
If you have a sealed system or combi boiler in your home, low water pressure might be to blame for your lack of hot water.
Modern boilers require constant water pressure in order to work properly. Low boiler pressure can cause your system to cut out, preventing your central heating from working.
The good news is that it’s easy to identify low pressure, and you can sometimes address it yourself.
As a rule of thumb, your boiler’s ideal water pressure is between 1.0 and 1.5 bars. To check this, you need to look at the pressure gauge which is located on the front of your boiler.
A digital pressure gauge will flash to alert you if your boiler has a pressure problem.
But if you have a hydraulic pressure gauge, you want the indicator needle to be in the green zone, between 1 and 1.5 bar.
When the pressure is below 0.5 bar, water has been lost from the system and needs to be replaced.
All boilers are different, so you should check your manual to see if you can re-pressurise your boiler yourself, using the filling loop.
If in doubt, you should contact a Gas Safe heating engineer for assistance.
9. No hot water: Check your pipes aren’t frozen
If your hot water has suddenly gone off when it’s freezing outside, there’s a good chance that your boiler’s condensate pipe has frozen.
The condensate pipe runs from the back of your boiler to an outside wall of your house. It’s responsible for taking waste from your boiler out into a drain.
If your condensate pipe freezes, your boiler will automatically shut off for safety reasons, leaving you without heating or hot water.
Thankfully, a frozen condensate pipe isn’t a big problem. You can easily thaw it out and get your hot water flowing again.
To melt the ice, you need to pour, warm (not boiling!) water down the length of the condensate pipe. Once the pipe is thawed, you should rest your boiler.
Wait a few minutes and check your water. If you have fully thawed your frozen condensate pipe, everything should be working as normal.
10. No hot water: Check for leaks
A leak somewhere in your heating system can cause the pressure to drop, which can stop your hot water from working.
And just because you’re not wading through water, doesn’t mean you don’t have a leak! Some leaks can be very small, resulting in a more gradual drop in pressure.
Have a look around your home for telltale signs of a water leak. You should look for damp patches in the following places:
- On ceilings;
- Around your boiler;
- Close to pipes;
- Beneath your radiators.
If you find a leak, you’ll need to contact a Gas Safe engineer for assistance.
11. No hot water: Check your diverter valve
If your radiators are getting warm, but you have no hot water, there’s a chance that there’s a problem with your boiler’s diverter valve.
A key component in a combi boiler is the diverter valve. It allows your boiler to switch between hot water for your taps and your central heating. If it fails, then one of those systems is going to lose out.
If your diverter valve has developed a fault, it could be stuck in the central heating position, resulting in your lack of hot water.
Unfortunately, a problem with the diverter valve is not something you can deal with yourself. You’ll need to call a Gas Safe registered engineer to fix it or replace the part altogether.
Will I need a new boiler?
If you’ve experienced a sudden problem with your hot water, it’s very unlikely you’ll need a new boiler. As you can see from above, there is often a cheap and quick fix to the dreaded no-hot-water situation.
But if your problems with hot water have been more gradual and subtle, it might be worth considering a boiler replacement.
It’s definitely worth getting a heating engineer to look at your system and advise you on whether you would benefit from a new boiler.
We hope that this guide has been useful in helping you to troubleshoot some of the simpler causes of having no hot water.
As with all things, prevention is better than cure. The best way to avoid the unwelcome surprise of a cold shower, is to have your heating system regularly maintained by a Gas Safe engineer.
Having your boiler serviced annually will keep your boiler running smoothly and efficiently and will catch any minor issues before they develop into more expensive ones.
A survey in 2021 by Which? found that only around three in ten boilers that are serviced annually have needed a repair in their first six years. This doubles to around six in ten boilers if the boiler is only serviced every two to five years.
So, get booked in for that service!