A faulty diverter valve is a common problem with older combi boilers. Over time they can wear or break, causing havoc on central heating systems.
Today, we’ll cover:
- What is a diverter valve?
- Symptoms that highlight a faulty diverter valve on your boiler
- What should you expect from an engineer?
- The costs to fix a faulty diverter valve
It might be a simple fix, but diverter valves are expensive.
If you’d prefer to avoid expensive repairs, it might be worth investing that cash into a new appliance, and comparing new boiler costs here.
What is a diverter valve?
Here is what a diverter valve looks like (Worcester Bosch).
The diverter valve on a combi boiler works much like a lock on a canal would. It opens and closes to allow heat up both hot water and the water in the heating system which provides heat to radiators and towel rails.
In theory, the valve should always prioritise your hot water (water from taps and showers) over your heating system.
So, when you switch on a tap, the diverter valve will close off the heating supply until you have turned the tap off.
Since this is a moving part, a lot of diverter valve faults relate to the valve sticking.
Symptoms that highlight a faulty diverter valve on your boiler
#1 – Luke-warm hot water (taps and showers)
This is one of the most common symptoms of a faulty diverter valve. Luke-warm water will be supplied to showers and taps. The boiler should prioritise hot water, but if the valve is slightly stuck open on the heating side, some of the heating power (that is usually supplied to the taps and showers) is escaping.
#2 – You have to leave the heating on otherwise you have no hot water
If it’s a warmer time of the year and your heating is off, try turning it on and letting it warm up. Once it has, see if there is any hot water. If the temperature of the water increases after switching on the heating, this is another sign of a faulty diverter valve.
#3 – Lots of hot water but no heating
This is a common fault linked to a diverter valve. The diverter valve is likely stuck on the hot water side. So even though your hot water is a priority, the valve can’t open to allow the heating to warm up.
What should you expect from an engineer?
We never advise trying to fix a boiler, instead use a Gas Safe engineer.
An engineer will run a fault check to ensure that it is a faulty diverter valve, and not something else.
There are other boiler issues that can show similar symptoms.
If this is a new property, or the problem has always been present, it could be something as simple as valves (on the pipework) not being open.
This fault check will usually include checking to see that all controls are working correctly.
The engineer will likely replace the whole diverter unit. In many cases, it’s only the diaphragm that needs replacing, but labour costs mean it’s worth getting the whole unit replaced.
The last thing you want is to replace the diaphragm and then have to call an engineer back in the near future because the valve itself is sticking.
Whilst the boiler is in bits, it’s certainly worth having the engineer assess the other visible parts for wear and tear.
If there are not major issues, then the replacement of the faulty diverter valve is all that is needed.
When the diverter valve is faulty, and other expensive parts are on their way out, we’d suggest getting no-obligation quotes for a new boiler here.
Costs to fix a faulty diverter valve
Expect to pay £250-350 to have a faulty diverter valve replaced.
Like every other aspect of a heating system, there’s a lot that affects the cost.
The cost of the valve itself
First, the cost of the diverter valve.
If we take a quick look over at Google, we can see that valves fluctuate from around £80-200.
If you’re boiler has a diverter valve that costs £80-120, it’s likely £250 will cover the cost of the repair (including parts and labour)
If you’re boiler has a diverter valve costing £150-200, it’s much more likely to cost £275-350 to repair (including parts and labour).
The cost of labour
Hourly rates throughout the country vary. Being in a less expensive part of the UK, compared with say London, could make £50-60 difference to the overall repair cost.
Also, consider the ease of replacement. Some faulty diverter valves are easy to get to and easy to replace.
The quicker and easy the replacement is, the less it’s going to cost.
When you shouldn’t replace a diverter valve
Boilers that are 8-10 years old are certainly not as advanced as new boilers. We already know there is a diverter valve fault.
Get the engineer to check the rest of the boiler parts thoroughly.
Boiler manufacturers tend to offer warranties in the 5-10-year range, so you know you won’t have any problems during that time.