What is a diverter valve & how do they work?
A Diverter Valve opens or closes to provide hot water to your taps, or central heating depending on your preference at the time and a combi boiler can only do one at a time and this part is how it is controlled.
If your heating or diverter valve hot water supply is not working properly, you might need to replace the diverter valve and a combi boiler problem like this is more common if your boiler is old.
You may have heard of a diverter valve before but never really understood what it does or how it works. It is important to understand what you are buying and that only combi boilers have a diverter valve, while other types will require an external one.
This is the place to be if you’re interested in learning more about this part of your combi boiler and why your boiler isn’t working properly. Read on to find out more about what a diverter valve is and how they work!
What does a diverter valve look like?
Diverter valves may look different, but the one shown above is made by the German manufacturer Viessmann. This is a great example of the industry’s leading examples however there are many other brands that have similar designs, but they all have different levels of success and quality.
Third-party diverter valve manufacturers can also design components and repair kits that can be used across multiple boiler brands. There is a selection of diverter valves available made by different manufacturers. As with anything depending on how good the part is there will be differences in materials used for each component. Diverter valves that use plastic can cause long-term problems due to material degradation.
What is a diverter valve?
Diverter valves are used to turn on or off hot water at the taps, showers, or radiators. Turn on the tap if your central heating is on. The diverter valve will shut off central heating and redirect it to the taps.
This is how diverter valves function. They redirect the water to the correct outlet, regardless of whether it’s the central heating system or the shower and taps. If water is being fed to the heating system it will be going to the primary heat exchanger of the boiler. If the water is for hot water, it will go to the secondary plate heat exchanger. This will warm the water for your showers and taps and ensure that it is clean
The diverter valve is able to prevent hot water from coming from the same source as the central heating to prevent contamination
Common diverter valve problems – How to tell if you have a faulty diverter valve
Lukewarm Water
Your diverter valve may be faulty if the water coming out of your showers or taps is only lukewarm.
If you are having problems, this is one of the most common symptoms. It is more often caused by the valve getting stuck. It might get stuck because it is left open on the heating side. This means that hot water that should be going to the taps or showers may not be available.
Consider how this could affect your annual energy bills. Heat is lost more often, which means that more money is being wasted. combi boilers are extremely efficient so you will want to get this fixed as soon as possible.
No central heating but hot water working
This cold should not have been felt by anyone and if you have hot water from your boiler but the central heating isn’t working, this may be why:
This is the same reason as for the ‘lukewarm’ scenario. The diverter valve will likely be stuck on the side that provides hot water therefore the valve will not be able provide hot water if your taps are turned on. It can only send water to central heating.
No hot water
It’s possible that you are unable to get hot running water out of your taps but central heating is working. You might also want to test the temperature of your central heating. If hot water is not flowing through the tap until now, it could be a problem with your diverter.
A bad diverter valve could have many negative effects on the boiler’s components and it can lead to limescale buildup in your domestic hot-water supply. This can cause a buildup of magnetic sludge (which can be stopped by a magnetic boiler filter) in the water that goes through your central heating system. This causes your radiator to become cold at the bottom and requires a chemical flush or other similar process.
How can I test to see if the boiler diverter valve is working?
We recommend calling a Gas Safe registered engineer to inspect your diverter valve if you suspect it is defective. Although some checks are as easy as taking off the boiler cover to check for the diverter valves, it is illegal for you to do any boiler maintenance.
Can you free a stuck diverter valve?
We recommend calling a professional heating engineer to inspect the diverter valve. If you don’t take care, any work on a gas appliance can cause further damage to the boiler.
An engineer can perform checks to determine if the problem is caused by a defective diverter valve or another issue. The valve may have become stuck over time. After cleaning it with a commercial chemical cleaner, it can be re-fitted.
Depending on the severity, the engineer might recommend that you replace the valve. It is a good idea to check if your boiler has a warranty. You may be eligible to have your diverter replaced free of charge if it is under warranty. You will need to pay for the engineer’s time as well as the replacement valve, which can range from £60 to £250.
Sometimes it is more cost-effective to replace the whole boiler system. This can be true for combi boilers older than 10 years. After a thorough inspection of your system, your heating engineer can advise you.
What is the cost of a new diverter valve?
Diverter valve replacement cost can vary a lot.
Do not buy a low-quality product. Instead, make sure that your boiler has components that are durable.
Take a quick look on google. A diverter valve cost is around £200+. However, many manufacturers charge much more. This does not include the price of the part. The cost of labor can also be a factor, meaning that the price may go up.
Our average cost for repairs to older boilers is between £300 and £800. If further problems are discovered, multiple visits may be required. You could need to replace more components, which will cost you even more.
Your problem could also be due to the boiler’s diverter valve. The diaphragm is activated by the hot water supply pressure difference. This allows the water to be diverted. A worn-out component of your boiler can cause a problem like a punctured diaphragm. This can cause the boiler to not be able switch between the water supply for taps and central heating.
You shouldn’t put off buying a single component of your boiler. There’s always the possibility that another component could also be failing if it is too old. A replacement boiler may be the best choice if your boiler is more than ten years old.
Consider these things when you are considering a repair.
You need to consider other factors, besides the cost.
- Callout fees will apply, normally between £50 and £150 depending on the location and company size
- The typical repair or replacement of a component like this takes between and to complete.
- The cost of labor varies depending on where you live and the size of your company. Local installers in London can charge more than those located further away and farther away.
Every manufacturer makes their boilers differently. This means that the process of replacing boilers can vary depending on which one you are dealing with.
All this being said, it is worth seriously considering whether you want to spend hundreds of pounds on a boiler without a warranty. You could be stuck if components fail.
What age boiler should you consider replacing?
A faulty diverter valve could be the problem if your boiler has reached a decade of age. It can be hard to predict how long it will last, even if the repair is minor. You could spend anywhere from £150 to £500 on a basic repair. Do you need to ask yourself Are the costs for a boiler repair that high?
You might consider the possibility of getting a completely new boiler if you don’t want to spend hundreds on a part.
