How to Fix a Faulty Diverter Valve

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There are many things that can go wrong in combi boilers, but one of the most common faults that always makes itself known quickly is a problem with a diverter valve. 

The diverter valve performs a hugely important task, and that’s why you’ll soon realise if it isn’t working as it should. 

In this article, we’ll explain more about what a diverter valve is and what it does before taking you through some of the clearest signs that your diverter valve could be faulty. 


What is a Diverter Valve?

All combi boilers have what’s known as a diverter valve. As the name suggests, this valve performs the important task of diverting water wherever needed. 

The valve opens and closes according to signals given by the system. As it changes position, water is either sent straight to radiators or showers and taps. 


How Does a Diverter Valve Work?

Diverter valves allow combi boilers to provide hot water to radiators, taps and showers as and when needed. 

The mechanism behind these valves is relatively simple. When open, diverter valves allow water to flow through to all radiators in a system. But if someone switches on a tap or a shower, the valve will close to send hot water there instead. 

Water passes through the diverter valve to be heated by the main heat exchanger. If the valve shuts, the water will go to the plate heat exchanger instead. It will then be heated to a sufficient level to make it suitable for hot taps and showers. 


How Do I Know If My Diverter Valve is Faulty?

Several clear signs indicate a potentially faulty diverter valve. One of the most common faulty diverter valve symptoms is lukewarm water coming from the taps. 

You might also have a faulty diverter valve if you find that you have hot water but no central heating, or you can only get hot water from your taps if you also have the heating on. 


Your Water Isn’t Heating Up Enough

If your hot water has been running for a while, but it doesn’t seem to be reaching the temperatures it usually would, the diverter valve could be the culprit. Lukewarm water often results from faults in the diverter valve. 


You’ve Got Hot Water But No Heating

If you have all the hot water you need, but your central heating doesn’t seem to be working, you may also have an issue with the diverter valve. 

This scenario suggests that the boiler itself is working, but something is stopping water from flowing through to the radiators. And that something is quite likely to be the diverter valve if it isn’t opening and closing as it should. 


You Have to Leave Your Heating On to Get Hot Water

We often get calls from customers who have noticed a strange issue with their heating and hot water, meaning they need to leave their heating on to get any hot water from the taps. 

This often isn’t quite as noticeable in winter when the heating is on more, but during the summer months, it can cause real problems. Usually, a faulty diverter valve will turn out to be the cause of this problem. 


How Do You Repair a Faulty Diverter Valve? 

Thankfully, diverter valves can quite often be repaired without the need for more extensive work on your boiler and heating system. 

But this isn’t something we’d recommend you attempt yourself. Gas appliances can be incredibly dangerous when not handled correctly, so it’s always worth calling in the experts for repairs like these. 

If one of our engineers spots a faulty diverter valve, they may be able to fix it simply by removing the valve and cleaning it with chemical cleaning agents, before refitting it. In many cases, this is enough to get the valve moving as it should. If the fault is more severe, an engineer might have to replace the valve completely to get the heating and hot water working properly. 

Faulty diverter valves will rarely break the bank. In some cases, you might not have to foot the bill at all. You may be lucky and find that your boiler is still under warranty, for instance. If this is the case, your diverter valve will be repaired or replaced, with any costs fully covered by the company you bought it from. 

Sometimes it’s more economical to replace a boiler entirely rather than repair or replace a diverter valve. 

This is usually the case if the boiler is coming to the end of its life anyway, but it’s something to consider if your boiler is over ten years old. You were already thinking of switching to a more modern and efficient option. 

Get Advice on Faulty Diverter Valves

Whether you’re confident you’ve got a faulty diverter valve, or there’s an issue with your heating, and you have no idea what’s causing it, our team is on hand to help. We provide a full range of boiler repairs and services all over London. 

Our team of highly qualified, professional, Gas Safe Registered (CORGI) engineers are available 24/7 to help with everything from boiler emergencies to planned upgrades and replacements. 

Get in touch to find out more about the services we offer.