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Common Viessmann Boiler Problems and Repairs

Viessmann boilers are reliable and efficient appliances but that doesn’t mean they won’t encounter problems from time to time. Like any heating and hot water system, your Viessmann boiler works hard to heat your home and provide you with plenty of water, especially during the cold winter months. The majority of issues will require you calling in a qualified Gas Safe registered engineer, however, some Viessmann boiler problems, such as defrosting a frozen condensate pipe or topping up the water pressure, are simple to sort and can be solved without the need to contact a professional.

Below is a list of the most common Viessmann boiler problems and repairs, as well as advice on what you’ll need to do next when your boiler encounters each issue.

1. No hot water

If your heating is working fine but you have no hot water, the culprit could be a faulty diverter valve. Other common causes for hot water problems include low pressure, a leak or an issue with your power supply or water supply.

What to do next: The first thing you can do is check your power supply by testing light switches and sockets in your home. If the power is fine, check your water supply and gas supply as well. You can also check the boiler settings and timer to see if the hot water is set to the right temperature and the time control panel is active for hot water. If you still have problems after checking the power supply, water supply, gas supply, the boiler settings and the timer, then you’ll need to get help from a Gas Safe registered engineer.

2. Boiler won’t ignite

If your Viessmann boiler won’t fire up, there’s a good chance the burner is blocked by debris or it could be that there’s a fault with the air pressure sensor.

What to do next: Some Viessmann boilers will display the F5 fault code when the boiler burner becomes blocked. If this is the problem, the burner needs to be looked at and cleaned. To ensure the burner is inspected and cleaned safely and properly, you’ll need to call in a qualified Gas Safe registered engineer. If your engineer finds that the burner is not the culprit, they can test the air pressure sensor whilst inspecting your system.

3. Boiler is leaking water

Water dripping from your boiler is a serious problem that needs to be dealt with right away. Viessmann boiler leakages are often caused by internal issues, cracks in the boiler casing, loose joints or high water pressure.

What to do next: Switch off your boiler and get in touch with a Gas Safe registered engineer to diagnose and repair the problem. A boiler leak could be potentially dangerous and an extremely expensive issue to fix if not rectified quickly.

4. Low boiler pressure

If the boiler pressure is too low (below 1 bar), there could be a water leak in the system. Sometimes bleeding your radiators can cause the boiler pressure to drop, so this could be the culprit if you’ve bled your radiators recently.

What to do next: Before you do anything else, inspect all of the radiators and visible pipework to see if you can find a leak. Found a leak? Then you should contact a Gas Safe registered engineer. If you can’t find a leak, you can re-pressurise the boiler yourself, provided it is safe and you feel confident to do so. You’ll need to take a look at the boiler manual to check the correct pressure level before you attempt to re-pressurise it. If re-pressurising the boiler doesn’t fix the problem, call in an engineer to inspect the inside of your Viessmann boiler.