How does a Vaillant diverter valve work?

A diverter valve is an important part of modern combi boiler design. Knowing how this valve works in a Vaillant boiler will give you a better understanding of what you will need to do if you encounter a problem with it. That’s why in this blog we’ll be exploring how a Vaillant diverter valve works, how you’ll know if it’s not working as it should be, and the steps you should take to resolve the problem and get your boiler up and running effectively as quickly as possible. 

What is a Vaillant diverter valve and how does it work? 

The role of a diverter valve in a Vaillant, and any other type of boiler, is direct where the hot water goes in your heating system – whether that be the radiators, taps or showers. It is only found in combi boiler systems not conventional ones as the latter stores hot water in a storage cylinder. So, the valve is not required like it is in a combi system that heats water on demand. 

If you turn on a tap while your central heating is on, the diverter valve will prioritise sending water to the tap until it’s turned off. This is a prime example of how diverter valves work. They send the water to where it needs to go as and when you require it. When the water is being directed to the heating system it will go to the primary heat exchanger. If it’s needed for your hot water supply, it is diverted to the plate heat exchanger.

How can you tell if there’s a problem with your diverter valve? 

The diverter valve in a Vaillant combi boiler is known for being somewhat of a weak point in a generally good system. Its design centres around a pin that moves in and out to activate a small pin via a small motor. The O ring seal that surrounds the pin has a tendency to leak, which results in pressure dropping and problems for homeowners. 

This type of diverter valve is part of a combi boilers with an indirect design, and it’s not just Vaillant that has used this approach. In fact, most combi boilers available today are based on an indirect design, meaning they have diverter valves and like Vaillant’s are prone to leaking. You will know that your diverter valve is faulty if you experience one of the problems below: 

• You have access to hot water, but your radiators are cold – your valve might not be working properly if water is getting to your taps but not your central heating. 
• There’s no hot water coming from your taps – another indicator of a problem with your diverter valve is that you’re only getting lukewarm water from your taps. If this is the case, it’s likely that the valve is stuck and only a small amount of hot water is getting through to your taps. 
• The hot water only comes on when the central heating is on – sometimes a problem with the diverter valve doesn’t get discovered until the warmer months when you’re not using your central heating. If hot water is only coming out of the taps when the boiler is on, your valve is likely not diverting water properly. 

What to do if you suspect your diverter valve is faulty

If you have a problem with your diverter valve, you will need a qualified engineer to either repair or replace the part depending on the age of your boiler and the severity of the fault. In the case of older Vaillant boilers it might not be worthwhile repairing the valve and instead just buying a new one. However, if your boiler system is still relatively young you could buy a Vaillant diverter valve repair kit from NBS. We specialise in providing high quality new and refurbished boiler parts at affordable prices. Find the diverter valve product you need from our online store today.