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Boiler Repairs

By Matthew Knight

In need of a boiler repair? Read on for our expert tips on boiler repairs and maintenance.

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If you’re looking for a competent engineer to repair or service your boiler, you can find a trustworthy, local heating engineer by checking Which? Trusted Traders.

Which? Trusted Traders is a free service for all. It shows reputable traders in your local area that have been endorsed by Which?.

If you need a boiler service, make sure you download our free boiler service checklist and find out what happened when we installed hidden cameras to watch engineers servicing a boiler. Go to getting a good boiler service.

Otherwise, keep reading if you want to learn some easy things you can do to help keep your boiler in good working order.

Boiler repair

Any boiler repairs need to be conducted by a trained professional and should not be attempted by anyone who is not a professional heating engineer and Gas Safe registered. Attempting any repairs yourself or getting in someone who's unqualified is dangerous and is also likely to invalidate any warranty that you have on your boiler. 

That said, there are some simple steps you can take to maintain your boiler. Keep reading to find out what you can do before you have to pay out for a heating engineer to fix or properly service your boiler.

Boiler manuals

In an emergency, you may need to find your manual in a hurry. If you’ve lost it, you can contact the manufacturer. Check the model number on your boiler first to ensure you get the right instructions. Most manufacturers allow you to download manuals directly from their websites.

Boilers’ automatic pump anti-seize function

Most modern gas combi boilers should have this. The automatic pump anti-seize function automatically spins the pump for a few minutes when the boiler has not been in use for a long time. This helps prevent problems when starting the boiler up at the beginning of winter.

Boiler equipment costs

Radiator keys and carbon monoxide detectors can be found in most DIY or hardware stores. A radiator key usually costs around £5. A carbon monoxide detector typically costs between £15-30.  

Our lab tests have revealed detectors that fail to sound the alarm in the event of poisonous levels of carbon monoxide. To find out more, see our carbon monoxide detector reviews.

My boiler's condensate pipe has frozen. What can I do?

Boilers retain condensate water and then let it out in a gush in an attempt to prevent freezing, but the condensate pipe can still freeze in very cold weather. Particularly if the condensate pipe is external. 

If your condensate pipe is frozen up, your boiler will probably switch itself off - exactly the opposite of what you need in such weather. Follow these steps to get your boiler going again.

  1. Use warm, but not boiling, water to unfreeze the pipe's contents. This will only be a temporary fix 
  2. Lag the pipe with insulating material
  3. The pipe may need to be reinstalled if it's very narrow or at a shallow angle. The larger and more vertical the pipe is the better.

Open-vented boilers

Checking the flame

On older boilers – typically those more than 20 years old – you should be able to check the pilot light. There will normally be a see-through window that allows you to see the flame. If your boiler is combusting properly the flame should be blue. If it's turned yellow, you’ll need to call out an engineer.

If your pilot light goes out, consult your boiler manual to find out how to turn it back on again. Typically, this will involve holding down the reset button and clicking the ignition switch.

After the flame reappears, you’ll most likely need to keep the reset button held down for at least 30 seconds before releasing it. If this doesn’t work after a few attempts, you should call out an engineer.

No heating or hot water

On an open-vented system, if the pilot flame is lit but you don’t have any heat or hot water, you may find the ball valve is stuck in the feed and expansion tank.

Typical symptoms include upstairs radiators being cold, and no air or water coming out of them if you try to bleed them. The circulation pump may also be particularly noisy.

If you go to the feed and expansion tank (normally next to your cold water tank) and find it's empty, try moving the ball valve up and down. The valve should start working again, and the feed and expansion tank should start to fill up.

Save money with a new sealed system

Older, open-vented non-condensing boilers take air in from inside your home. Newer, sealed condensing systems take air directly from outside. This means that a newer sealed condensing boiler will normally take in cleaner air and be better at retaining energy.

A new sealed condensing boiler will be at least 25% more efficient than an older non-condensing type.

Need a new boiler? We reveal the boiler brands you can trust - discover the best boiler brands.

Maintaining hidden boiler flues

Owners of room-sealed fan assisted boilers are being warned that they may need to make a hidden boiler flue easier to inspect visually. Otherwise their boilers may be turned off to avoid a risk of carbon monoxide poisoning.

The danger of hidden boiler flues

The flue is a metal tube that usually comes out of the top of a boiler and goes into the wall. It carries waste gases away from your boiler, which are released into the air outside. 

A flue in poor condition, combined with a boiler that's not working properly, could put you and your family in danger from carbon monoxide poisoning. This can cause death or serious injury.

Gas engineers need to be able to see the flue as part of the essential safety checks to ensure that there are no fumes leaking from it due to holes or poorly-fitting joints. Make sure your engineer does a thorough job - see our boiler servicing checklist.

If you live in a property that has a boiler flue that can't be inspected because it's hidden behind a wall, chimney or ceiling, you need to install an inspection hatch. Otherwise your boiler may be classified as 'At Risk' and turned off when inspected by an engineer.  

However, if your engineer can see all of the flue, you won't need to take any further action. If your boiler is situated on an outside wall, it's unlikely to have this type of flue. 

Why is carbon monoxide (CO) dangerous?

Around 25 people in Great Britain die each year from CO poisoning caused by faulty gas appliances and flues. 

CO is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels, including gas. It's only when the gas doesn't burn properly that dangerous levels of CO are produced. 

CO stops the blood from carrying oxygen round the body and can kill quickly. Symptoms include headaches, breathlessness, nausea, dizziness, collapse, loss of consciousness, tiredness, drowsiness, vomiting, pains in the chest, stomach pains, erratic behaviour or visual problems. To protect yourself and your family, install a carbon monoxide detector. This will alert you if there's a carbon monoxide leak.

Use our expert advice to find out more about installing and testing a carbon monoxide detector.

Do I need flue inspection hatches?

Gas engineers are required to be able to see the flue to inspect it. If your boiler is on an outside wall, it's unlikely you have a hidden flue. If your gas engineer can see all of the flue, then you don't need to take any further action.

If you do have a boiler where all or part of the flue can't be seen, then you or your landlord will need to arrange for inspection hatches to be fitted so the flue can be inspected.

Industry experts expect that 30,000 properties in the UK may be affected. Mostly those that were built between 2000 and 2007, or properties converted into flats around that time.

What if I don't install a hatch?

Since 1 January 2013, gas engineers who are unable to visually inspect the length of your boiler flue should advise you that it's 'At Risk' and will ask your permission to turn it off, to ensure they comply with industry guidance. This may occur if you call in an engineer to service or repair your boiler.

You can refuse to allow the gas engineer permission to turn off your boiler, but you will be asked to sign paperwork to confirm you accept responsibility for those defects identified in the system which could result in a serious incident.

How much will inspection hatches cost me?

It varies from property to property. Hatches should be at least 300x300mm and positioned within 1.5 metres of any joint in the flue system. The number of hatches you need will depend on how long your flue is. 

Basic inspection hatches must comply with the Building Regulations and are likely to cost from £75, although you may choose to fit more expensive ones for cosmetic reasons. 

Costs for fitting the inspection hatches will be extra.

Who do I approach to install inspection hatches?

A competent builder or building services company should be able to fit the inspection hatches. The builder will need to speak to a registered gas engineer to find out how many inspection hatches are needed and where they should be placed. 

You can find a recommended local builder using Which? Trusted Trader.



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