Is your boiler leaking water? Read this troubleshooting guide to help you diagnose the problem and get it fixed – quickly and hassle-free.
What’s in this article?
Why is my boiler leaking?
There are various reasons for a leaking boiler, and these will generally determine the cost of repairing or replacing the boiler or another part of the system.
Although you can use this guide to help you discover the problem, it’s wise to call a Gas Safe engineer as soon as you notice a leak to help reduce damage to the boiler or system.
Why is my boiler leaking from underneath?
How to check for boiler corrosion:
Get in touch with a gas engineer to visually check how corroded your boiler is, as some corrosion may be internal. In this case, you’ll need a gas safe registered engineer to remove the front of any gas appliance and carry out internal checks.
How to check for boiler corrosion:
Get in touch with a gas engineer to visually check how corroded your boiler is, as some corrosion may be internal. In this case, you’ll need a gas safe registered engineer to remove the front of any gas appliance and carry out internal checks.
How to fix boiler corrosion:
Again, it’s dependent on the amount of water damage that will determine if you need a repair or replacement. You can discover this by contacting a gas safe registered company and checking out the best online deals. Alternatively, contact our team of expert engineers to get a quick quote today.
I need a boiler replacement
Need a boiler replacement? At Boilerhut, we’re an accredited installer with a five-star rating on Trustpilot.
Click the button below to get a quote in minutes, and be one step closer to having your broken boiler replaced.
Not sure if your boiler needs replacing and want to find out more? Then why not read Should I Replace My Boiler?
Leaking boiler heat exchanger
Another reason your boiler may be leaking from the bottom is heat exchanger corrosion. Over time this type of corrosion can form splits that result in water leakage. The heat exchanger is an expensive part of a boiler and in most cases, unless your boiler is under warranty, it’s more cost-effective to get a replacement rather than a repair which would be considered uneconomical especially if the boiler is older than 10 years.
How to check for a leaking heat exchanger:
Only a qualified gas engineer can diagnose a problem with the heat exchanger. Need more information? Get in touch with our team of expert engineers to find out more.
How to fix a leaking heat exchanger:
As mentioned, replacing a heat exchanger is costly. The best option is to get a new boiler, Which best buy for 3 years running Viessmann 050 with a stainless steel heat exchanger that has a low chance of breaking, cracking or leaking.
Poorly installed pipework
On the other hand, if your boiler has just been installed or isn’t particularly old – then, clearly corrosion won’t be the cause and the leakage is more likely due to poor installation. It’s more likely that some of the pipework hasn’t been fitted correctly, resulting in water escaping.
Don’t panic – this issue is easily corrected! Small water leaks are common in most installations, especially if you’ve gone for price over quality. Any reputable installer will return to correct any work and fix those leaks.
Need an expert installer? We’ve flawlessly installed thousands of boilers across the UK, ensuring everyone gets the best boiler, at the best cost. Sounds too good to be true?
Just take a look at what our customers say.
How to check for a water leak beneath your boiler:
Look directly underneath your boiler for any signs of water leakage, and feel around the joints of pipework for dampness. In some cases, there may be a dry joint which needs to be fixed, any plumber can deal with this situation.
Also, another way to check for leaks is to ensure the area is dry and you can place some kitchen towels under where you suspect the leak to be coming from. Sometimes small leaks on hot pipes can evaporate before forming a drip; this can normally be seen by a visual inspection as it leaves a white/green crumbly residue.
Why is my boiler leaking from the overflow pipe?
Pressure release valve issues
This issue typically affects combi or system boilers and is usually due to a problem with the pressure release valve (PRV). A relief valve or PRV is part of your boiler’s safety control, which is designed to limit pressure on the system, by releasing water when the boiler operates above its working capacity.
Combi and system boilers work at an optimum pressure of 1.3 bar, although anything within 1-2 bar will work without issues, if you exceed this load the system may overflow with water. Once the boiler overfills due to the filling loop, the pressure release valve will discharge any excess water to stop any other components self-destructing.
Condense pipe issues
In some cases, this could be due to the pressure release valve not being seated correctly, allowing water to pass by it.
It’s also critical not to confuse the pressure release valve with the condense pipe. The condense pipe is plastic and is meant to drip while your central heating is on or when you’re running hot water.
Some boiler manufacturers have combined the PRV and condensate into one pipe like Viessmann; this can be advantageous when installing a boiler in the middle of the house like the airing cupboard.
Check for pressure issues:
Most combi or system boilers have a pressure gauge on the front (see pictured). The pressure should be around bar 1 within the green markings, anything over that green bar or in the red bar indicates an over pressurised boiler.
Need some advice? We hear to help, just pick up the phone or drop us a line and we’ll help you troubleshoot your boiler concerns. Alternatively, you can read through: Why is my boiler pressure too high? to discover common pressure issues and how to fix them.
Ready for a new boiler? Then contact us today to receive your FREE personalised quote!
How to fix pressure issues:
Firstly, you should check that the filling loop tap underneath your boiler is firmly closed – to do this, push the black taps on the silver flexi-pipe (see pictured) all the way left or clockwise to firmly close.
Now, you can start bleeding the system to reduce the pressure.
Bleeding radiators (and instruction video)
To perform this, you’ll need a bleed key (see video) and a low level of confidence. Use the bleed key to loosen the nut on the end of the radiator. As you turn it, water from your system will come out.
Why is there water on top of my boiler?
This leakage may be due to the auto-air vent, which acts as another fail-safe component. When the boiler’s pressure is too high, the tension exists as air through the auto-air vent. This vent runs on pressurised valves these pipes can stick, resulting in water being released as well.
Typically, the water will drip from the top through and down the casing to pipes beneath the boiler. Generally, this will only apply to older boiler boilers and would arise in a pressurised system, such as a combi and sealed system boiler.
Also water leak ingress from a poorly installed flue can be condensate produced by the boiler or rainwater tracking down the flue. A gas safe engineer would be required here to carry out any work on flues.
Leaks from seals on internal parts
Sometimes, the seals on internal parts of your boiler can decay and fail, once the seal has broken water will leak out. This can lead to corrosion if not treated.
This can lead to complete boiler failure if not treated and it can run onto the electrical printed circuit board which is the brain of the boiler and expensive to replace.
How to check for leaks on seals:
Although you can remove the cover of the boiler and look around at home, we’d advise you to contact a registered gas safe engineer.
How to fix leaks on seals:
Most, small sealant issues can be resolved by a replacement part. But, if the damage has been caused by corrosion then you’ll probably be looking at a replacement boiler. To discover the root of the damage you’ll need to contact a gas safe engineer.
What should I do if my boiler is leaking?
Is a leaking boiler dangerous?
A leaking boiler can become dangerous if the water is dripping over electrical parts. Although most electrical units have seals, it would be wise to turn the boiler off and call an engineer.
Will a leaking boiler lose pressure?
A Leakage will prompt the boiler to lose pressure. In fact, any leak in the central heating system decreases tension.
How to prevent future boiler leaks
Ensure your gas engineer uses a magnetic boiler filter when fitting your boiler. These collect all-metallic system debris from your heating system, to help prolong the life of your boiler, limit blockages and prevent the risk of the boiler leaking.
Need to replace your boiler? Check out our best boiler to buy in 2020, to ensure you get the best system for your property.
How much will a boiler replacement be?
Get an online quote from Boilerhut if your boiler is old or you feel it is beyond economical repair.
Life expectancy for modern boilers if installed to manufacturer instruction and has a serviced by a qualified gas service engineer annually.
| Boiler type | Life cycle | Example boiler model |
|---|---|---|
| Budget Boiler | 5 to 7 years | Worcester Bosch Greenstar 25i Combi |
| Mid-range boiler | 7 to 10 years | Viessmann Vitodens 100-W Combi |
| Premium brand boiler | 10 to 15 years | Viessmann Vitodens 200-W Combi |
Boiler replacement cost guide
Below is the potential price of a gas boiler replacement in a property with 3 bedrooms. All of the totals in the table are averages and could go up or down.
| Boiler type | Average cost of boiler without installation | Average cost of boiler installation | Average total cost of boiler fully installed |
|---|---|---|---|
| Combi boiler | £500 – £2,000 | £500 – £1,000 | £1,000 – £3,000 |
| System boiler | £500 – £2,500 | £500 – £1,000 | £1,000 – £3,500 |
| Conventional boiler | £500 – £2,750 | £500 – £1,000 | £1,000 – £3,750 |
Boiler repair cost guide
We’ve designed a pricing estimate matrix that highlights the general replacement cost of boiler parts. Because replacement parts will vary in price depending on factors such as the model, brand, and type of boiler.
The repair costs below cover both parts and work.
| Boiler Part To Be Replaced | Replacement Cost |
|---|---|
| Fan | 245 |
| Pump | 250 |
| PCB | 350 |
| Heat Exchanger | 475 |
| Heat Exchanger | £300 |
| Diverter Valve | £350 |
| Overheat Thermostat | £180 |
| Timer | £100 |
| Ignition Leads | £200 |
| Gas Valve | £300 |
| Flue | £150 |
| Air Pressure Switch | £200 |
| Automatic Air Vent | £170 |
| Burner | £275 |
Another pricing factor to bear in mind is the cost of a gas safe engineer and the number of days the job will take. Also, if you require emergency work outside of normal business hours, you may be charged at a higher rate.
I need a new boiler!
Who Should I Choose to Replace My Boiler?
Look for Reviews
Excellent 5-star reviews are usually a good indicator of the service a boiler installation company provides. For example, Boilerhut is rated Excellent with almost a perfect 10/10 score on Trustpilot. Click here to read our reviews.
We specialise in installing high-quality A-Rated Gas, Oil, and LPG Boilers for homeowners, private tenants and businesses.
Our quoting system gives you a free, no-obligation online quote within minutes, which can be finalised within hours and installed within days. Our team then takes care of any service plans and warranty. We’re also Gas Safe and APHC Registered, Viessmann Premium Partners and PAS 2030 accredited. This means your installation will be carried out to the highest British quality standards, and because of our partnership with Viessmann, their engineer will be at your doorstep within 24-48 hours in case of any issues.
This gives you peace of mind and assurance that you are taken care of.
So when you ask “Who should I choose to replace my boiler?” The answer, as thousands of customers will tell you, is Boilerhut.
What next?
Hopefully, our troubleshooting guide to why your boiler is leaking water has helped. If not, head over to our boiler problems guide.
If it hasn’t – we’re happy to offer boiler help and advice by answering questions.
Just leave a comment below.
Bottom Line – a boiler that is leaking water can be hazardous and also costly to repair or replace. Take the time to evaluate the condition before taking action when it comes to your leaking boiler.