No hot water? Here’s what to check

1. Is your boiler working?

If your boiler has a fault, it will likely display as a fault code on the main screen. 

You can find a list of Viessmann’s fault codes here.

Some fault codes can be rectified yourself with a simple boiler reset, whilst others may need professional attention. If you are not sure how to fix the fault code, it is recommended that you contact a qualified engineer for advice.

2. Are the boiler’s settings correct?

A boiler has all kinds of settings, but there’s a chance you or someone else could have accidentally altered the settings, so you may want to make sure that the hot water is set to a reasonable temperature. Your hot water should be set to a minimum of 60 degrees on a hot water cylinder, a combi boiler can be variable and is down to preference.

3. Is it programmed correctly?

Things such as power cuts and low battery can have an impact on the timer, so you should check that the timer is set to the correct time and date, that it hasn’t run out of batteries and that it’s correctly programmed.

Finally, you should ensure that the boiler is currently programmed to both heat and provide hot water.

4. Is your energy supply ok?

You can check if your energy supply is ok by testing other appliances. For example, to see if the gas supply is working, you can try turning on a gas hob or fire. To check the electricity supply, turn your lights on and off or test some plug sockets. You should also take a look at your fuse box to see if any fuses are tripped, as this could affect whether you have hot water or not.

If there is a tripped fuse, you may wish to take our suggestions above and reset the boiler’s timer and programmes.

5. Is your water supply ok?

This may seem like an obvious fix, but you should also check that your home has a sufficient water supply. If you don’t have water coming from any taps, whether hot or cold, then there may be a temporary supply interruption. You could contact your water provider to see if they can help you out or give you any more information, or you could wait for normal services to resume.

6. Do you have a frozen pipe?

The condensate pipe is the one that carries waste water vapour away from your boiler and is most likely to freeze if it does not have the correct level of insulation at the point where it exits the house. Ice can form inside the pipe if it has frozen, you can use warm water to slowly defrost it.

7. Is the pressure too low?

The water pressure in the system should be around 1.25 bar. You will be able to see this by looking at the pressure gauge located on the front of your boiler. If the pressure is too low, you should repressurise the system by opening the filling loop to allow more water in. If the pressure is too high, you may need to bleed the system slightly to bring it back down to within the normal range. 

8. Is there a water leak?

A leak in your heating system can cause a fall in pressure which, as we know from above, can cause your boiler to shut down. Check for signs of a leak, including water on the pipes around your boiler and damp patches on walls or ceilings.

9. Is there an issue with the diverter valve?

The diverter valve is the part of your heating system that allows the boiler to switch between hot water and heating, depending on what the system has been programmed to do. If the diverter valve is not working properly, it could be stuck in the central heating position or may have developed a fault, and either of these issues can result in a lack of hot water.

If there is a problem with the diverter valve, you’ll need to call a Gas Safe registered engineer to fix it or replace the part altogether.

10. Is your boiler big enough?

If you have eliminated any fault in the system and you have a recurring problem with your hot water supply, the issue may be that the boiler simply isn’t big enough and is struggling to provide enough heat and hot water for your house.

In the long term, it may be cost effective to upgrade to a larger boiler if this is the case. An expert will be able to advise you of the optimum boiler size for your home based on your current and future needs.

Still got no hot water?

If you are confident that your hot water problem is not caused by one of the above problems, then it may be advisable to seek help from a trained Gas Safe engineer.