Vaillant Boiler Repairs

Find out the most common Vaillant boiler repairs and problems

In case you’re unaware, Vaillant is a Which? Best Buy winner with an overall score of 80%. This is great news if you’re about to get a Vaillant boiler installed because it means that you’re investing in one of the most reliable boiler brands around today. But like all boilers regardless of brand, Vaillant boilers can still become faulty at times and end up needing a professional repair.

Now, we’re not going to lie. The majority of Vaillant boiler repairs can only be resolved by a qualified and Gas Safe registered engineer. There are some simple problems you can safely rectify yourself though, provided you feel confident to do so.

Below, you can find the most common Vaillant boiler repairs and problems, their possible causes and the best way to deal with them.

Common Vaillant Boiler Problems

1) Boiler is not providing heat for radiators

This is probably an issue with your radiators, rather than your Vaillant boiler. The most common cause of cold radiators when your heating is switched on is trapped air in the radiators. Thankfully, this is something you should be able to fix without the help of a professional.

How to deal with it:Put simply, you need to bleed your radiators to remove the trapped air. Don’t know how to bleed your radiators? Don’t worry. We’ll walk you through each step.

• Find a radiator bleed key. If you don’t have a key at home, pop to your local DIY store to purchase one.
• Turn your heating on so that you can identify which radiators are not getting any heat. You should still do this even if you know which radiators are not warming up as it will push the trapped air to the top of your radiators.
• Switch off your central heating and double check that your radiators are still cold.
• Grab a cloth or towel and your bleed key and choose a cold radiator downstairs to start working on. You could also take a bowl with you.
• Open the radiator bleed valve (don’t open it fully) using your bleed key and hold a cloth beneath the valve to catch any drips of water. The bleed valve is usually located either top left or right on your radiator. To open the bleed valve, slowly turn the key anti-clockwise.
• Keep turning the key until you hear hissing and see a steady stream of water.
• When the hissing stops and the water begins to just trickle, turn the key clockwise to close the bleed valve. Be careful not to close the bleed valve too tight as this could damage it.
• Repeat this process on each radiator that has not been heating up. It’s best to start working on the radiators downstairs and work your way up to the top floor of your home.
• After bleeding all of your radiators, re-pressure your Vaillant boiler before switching it back on.

If you find that your radiators are not heating up after bleeding them, you’ll need to get in touch with a qualified engineer.

2) Boiler pressure is too low

If you’ve noticed that your pressure gauge is less than 1.0 bar, you definitely have a low boiler pressure problem. This needs to be sorted out straight away because it could be that your Vaillant boiler has overheated, which can lead to fried boiler components and additional costly repairs. That said, low pressure can be caused by trapped air in your radiators, a faulty expansion vessel or even a leaking diverter valve.

How to deal with it:There are a couple of things you can try before calling in an engineer including re-pressurising the boiler and resetting it, as well as bleeding your radiators to get rid of any trapped air. Your boiler manual should explain how you can top up the boiler pressure but you can get an engineer to do this for you if you don’t feel comfortable carrying out this simple fix. If the boiler pressure is still too low after a boiler re-pressure and radiator bleed, an engineer will need to inspect your system.

3) Boiler won’t start up

A Vaillant boiler that is refusing to ignite could be due to an issue with your gas supply issue, which is nothing to do with the boiler itself. However, it could be that you have a faulty gas valve or ionisation probe.

How to deal with it:The only thing you can do is check that your mains gas is on by seeing whether your other gas appliances (like your cooker) are still working properly. If it turns out that you haven’t any gas at all, you should contact your gas supplier to find out why this is the case. Don’t forget to check that you have credit if you use a prepayment gas meter as you may not realise that it needs topping up if you’ve been using more gas than usual. If no gas supply or lack of credit isn’t the problem, an engineer will need to take a look at your Vaillant boiler.

4) Hot water temperature fluctuates

If your water temperature keeps switching from hot to slightly warm when you’re in the shower, the likely culprit is a blocked heat exchanger. Sometimes, particles of dirt and rust can make their way from your radiators into your boiler and block the heat exchanger, which usually means your system is in serious need of a power flush or you need to replace your radiators.

How to deal with it:You are going to have to seek professional help with this one. An engineer will be able to tell you whether your central heating system just needs a power flush or some replacement radiators. It may even be that it’s just a fault with the heat exchanger but you’ll still need to call in a Gas Safe registered engineer to know for sure.

5) Water leakage around the boiler

One of the main causes of water leaks around a Vaillant boiler is leaking combustion seals. This is quite a serious issue as it can cause your boiler to overheat, which can result in severe damage to the internal components. Another cause of water leakage is leaking diverter valves or a fault with one of the other internal components.

How to deal with it: This is a Vaillant boiler repair that can only be resolved by a qualified engineer because they will need to repair or replace one of the components, which is something an unqualified person is not legally allowed to do.

Hire a Gas Safe and Experienced Vaillant Engineer

When you need help with fixing your faulty Vaillant boiler, it’s important to choose an engineer who is Gas Safe registered and fully qualified to work on boilers. We know it can be stressful when your boiler stops working but you must take the time to check the credentials of an engineer before allowing them to enter your home and repair your unit. To find out this information, either visit the Gas Safe Register website or ask the engineer to show you their ID card. It’s also wise to choose a professional with experience in carrying out Vaillant boiler repairs for peace of mind that they have the expertise to fix your boiler safely and efficiently.