Common Vaillant Boiler Problems and Repairs

Vaillant is well-known for providing homeowners with reliable and energy-efficient boilers, which explains why so many people love their Vaillant appliances. Boasting an excellent reputation for quality and performance, the brand has been manufacturing robust boilers for many years, making them a great choice for all property types and sizes. But like all other makes of boilers, Vaillant boilers must be regularly maintained so that they do not suffer a fault or breakdown and require expensive repairs.

If you’re experiencing an issue with your Vaillant boiler, read our guide to the most common Vaillant boiler problems and how they can be fixed.

1. Frozen condensate pipe

A frozen condensate pipe is an extremely common problem during the winter, particularly for modern combi boilers and if some of your condensate pipework is located outside. Not only can a frozen condensate pipe cause your boiler to make strange gurgling noises but it can also stop your boiler from working altogether. 

What to do next: The good news is that you can tackle this problem yourself, but only if you are confident to do so. You’ll need to put some warm water in a bowl or prepare some warm (not boiling) water using a kettle, then head outside to locate the condensate pipe. You can use a hot water bottle if you prefer. Once you’ve found the pipe, thaw it out by pouring the water over the frozen section or by placing the hot water bottle onto the pipe. Wait until the ice has melted, then reset your boiler (check the manufacturer’s instructions) to see if it’s working again. If you don’t want to thaw the pipe yourself or your boiler still won’t work after thawing the pipe, contact a Gas Safe registered engineer.

2. The water pressure is too low

One of the most common Vaillant boiler problems is low water pressure, but this is an easy fix and something you can resolve yourself. When the water pressure is too low, you may find that your Vaillant boiler displays the F22 fault code. Having said that, your low water pressure issue could be due to a leak, which is something you shouldn’t attempt to fix yourself.

What to do next: Check to see if your boiler is leaking or if there is a leak coming from one of your radiators. If this is the case, you will need to get an engineer to take a look and fix the problem. If you can’t find a leak anywhere in your home, you can re-pressurise your system by following the instructions in your boiler manual. Before you start, make sure you turn the boiler off and wait for it to cool. If the problem persists after you’ve re-pressurised the system, you’ll need to get in touch with a qualified engineer.

3. The boiler keeps switching off

This could be the result of low water pressure, thermostat issues or lack of water flow.

What to do next: See if the water pressure is too low and, if it is, see what to do next by reading common Vaillant boiler problem number 2 in this guide. If the water pressure is fine, check the thermostat as it could be broken and may need replacing, which is something only a qualified engineer will be able to do. You can also bleed your radiators to get rid of any air that may be trapped in the system. If the water pressure and thermostat don’t appear to be the issue and you have bled your radiators but the boiler still switches itself off, it could be that the boiler pump or another component is broken. By law, only a Gas Safe registered engineer is allowed to take apart your boiler and fix or replace any faulty components.

4. The boiler won’t ignite

If your Vaillant boiler is failing to ignite, the F28 fault code might appear on your boiler and the problem could be the result of a frozen condensate pipe or faulty ignition lead. However, it could be that there is a problem with the gas supply.

What to do next: First check that your other gas appliances are working to rule out any problems with the gas supply. If your other gas appliances don’t work either, you’ll need to contact your gas supplier. Still got gas? Then you should next check to see if you have a frozen condensate pipe. To thaw the pipe, read what to do next under common Vaillant boiler problem number 1 in this guide. If the gas is fine and the condensate pipe isn’t frozen, you should call out a Gas Safe registered engineer to find the cause and fix the problem.