Speak To Us Now   0208 964 6710

Vaillant Boiler Faults

The Staunch and Flow plumbing team provide specialist Vaillant boiler repairs across London. We’re accredited installers and have a substantial depth of knowledge of Vaillant boilers – including all the common Vaillant boiler fault codes seen across the range.

The team can take care of everything from boiler maintenance to completely new boiler installations. This includes boiler repairs and fitting parts. If your boiler is outside its guarantee period, Staunch & Flow engineers can get it working again – and each repair includes a Gas Safety Check as standard.

Staunch and Flow engineers are Gas Safe (Corgi Registered) plumbers. We are specialised in diagnosing not only Vaillant boiler faults but also repairing any other kind of boilers correctly and efficiently. Find out more about our boilers and heating service and plumbing services if you have a breakdown or need your boiler or cylinder serviced or repaired.

What boilers can you repair?

Our plumbers are trained to work on all brands, models and types of boilers. However, in this section, we are only addressing the Vaillant fault codes that are associated to Vaillant boilers. This includes F22, F28 and F75 faults and the issues associated with these.

How much does it cost to repair a Vaillant Boiler?

Staunch and Flow conduct repairs based on our hourly rate (£85+VAT+expenses/parts). Usually we can diagnose (and hopefully fix) the more straightforward problems in about an hour, but some issues will take longer to pin down and subsequently fix. We’ll only suggest the installation of a new boiler if is uneconomical to fix your existing unit. We’ll explain what the problem is and the options (where there are more than one) for getting your boiler up and running again. We only charge for the work that we do and, having done the work, we’ll provide you with any replaced parts. All of our plumbing engineers are registered Gas Safe, and are considered to be among the best plumbers in London.

Remember that the Vaillant fault code only gives an initial indication of what the issue might be. The underlying problem could be in a different part of your heating or plumbing set-up. Therefore, the first step for our engineers is to visit the premises, examine the boiler and, if necessary, the heating and water system as well, until the problem can be pinpointed. The only situation in which our staff would consider a “quick fix” is if the necessary parts need to be ordered and it’s essential to try to keep the system running until these arrive and can be fitted during a subsequent visit.

What are the most common Vaillant boiler faults and error codes?

Vaillant F22 Boiler Fault

This code is associated with a lack of water or low water pressure. If the boiler sensors detect a drop in the water pressure in the system, this error code may display, along with a red light. It will cut the ability of the boiler to heat water to a very low level, to avoid internal damage to the boiler’s systems. It is common in some Ecotec Pro and Ecotec Plus models.

If you have a filling loop, it can be used to top up the water pressure and this should allow the boiler to work at full capacity again. BUT it is important to realise that if the water pressure has dropped in the first place, there must be a reason for this. It is this underlying issue that the engineer should be contracted to fix – otherwise, the pressure will drop again, the boiler will shut down again, the pressure will be topped up and the same cycle will keep on repeating. If nothing else, the dose of inhibitor (to prevent rust and sludge build-up in your heating pipes and radiators) that should be in your system will become increasingly diluted, decreasing its effectiveness.

So, once we have determined whether the problem is related to a lack of water or a lack of pressure (or both), the engineer can look for the cause. The most common cause for a boiler losing pressure is a leak. This could be anywhere in the system – pipework, joints, vents, radiators, expansion vessels or even the boiler itself. Another potential cause is air in the system, usually building up in the radiators. Some older Vaillant boilers use a brand of water pump that was prone to faults or failure and this could need to be replaced.

Vaillant F27 Boiler Fault

This code is associated with the boiler’s sensors indicating that the burner flame is not conforming to expectations and could be triggered by several potential faults.

  • The gas valve is not functioning correctly, so the burner in the boiler isn’t receiving enough gas to produce the correctly calibrated flame.
  • The boiler’s “brain”, its printed circult board (PCB), might have been damaged or has malfunctioned, but the actual burner flame is OK.
  • The boiler’s flame sensor is damaged or has malfunctioned and needs replacing.
  • If the boiler isn’t firing up at all, then it’s possible that the ignition leads are faulty and need replacing, or the spark electrode is dirty and needs to be cleaned.

A diagnosis should be reached once the engineer has checked the various components of the boiler. Depending on the age and condition of the boiler, it may be cost-effective to simply replace the damaged/defective part. However, if the fault relates to the PCB, it may be more economical to replace the boiler, as it could cost hundreds of pounds to fix, but the boiler’s overall life expectancy might only be one or two more winters.

Vaillant F28/F29 Boiler Fault

These fault codes are related to a lack of gas, so will display after you have a boiler shutdown (lockout). Because this is related to the gas supply, on no account should you try to fix this yourself. A Gas Safe engineer will need to assess and fix such a fault. The only thing that you can try, if you have any other gas appliances, is to see if these still work (or not). Do you have a pay meter for your gas supply? Has it run out of money? Has your supplier cut off your gas, or are there repairs taking place to the gas main in your street?

Upon arrival, the engineer will be looking at the gas valve (whether it is working and has been set up properly), the ignition unit and leads in the boiler and the air inlet to the boiler.

Vaillant F75 Boiler Fault

This code relates to the boiler’s water pressure sensor and/or the pump and can be triggered by air in the system or a low pressure reading.

This fault is common on the Eco Tec Plus and Eco Tec Pro range. The underlying issue can be the pump and/or the pressure sensor, but it’s most likely to be a problem with the pump.

Some older Vaillant boilers used an unreliable brand of water pump. If you can’t hear the low hum of the water pump that characterises a working boiler, once the flame has ignited, then it’s a good sign that the pump isn’t working. It may be that the bearings have seized (common if the boiler hasn’t been used for an extended period). If it is the pump, then replacement is usually a good option.

The other possibility is that the boiler’s pressure sensor has malfunctioned. For a time, Vaillant used components that were not durable, and the sensors were revised numerous times in a short period.

This sensor has to cope with a likely build-up over time of a good deal of debris, which can hinder operation. Depending on what the engineer finds having examined your boiler, a pump replacement will cost around £300 and a pressure sensor around £250