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Common ATAG Boiler Problems & Repair Advice

Rob Wells
By: Rob Wells
Updated: 12th January 2022

Last Updated: 12th January 2022

ATAG Boiler Repair Advice

Some common ATAG boiler problems can be resolved without even having to call an engineer out but if an engineer is needed, (and if in doubt always get in touch with an engineer) you can get a free boiler repair quote with our service.

Most common ATAG boiler problems

Top 5 ATAG boiler problems ATAG error / fault codes
Igniting when heating is off Check thermostat
Low boiler pressure 118
No heating or hot water 133, 501
Radiators not heating up 133
Heating but no hot water 141

Igniting when heating is off

Digital wireless room stats could lead to your ATAG boiler turning on unexpectedly – potentially wasting energy when you’ve not made a call for heating or hot water.

How to stop the boiler randomly turning on

If this happens, double check that the minimum room temperature setting is fairly low (8°C to 12 °C) because if it's too high then when the room temperature falls below that temperature the wireless room stat will alert the boiler and heat the house up.

Low boiler pressure

This error code means that the pressure is less than 1 bar or pump pressure increase is too low (no pump detection).

Increasing low boiler pressure

Our guide to increasing boiler pressure can take you through the steps to get your ATAG boiler back up to the appropriate pressure

No heating or hot water

Possible causes can be broken diaphragms and airlocks, issues with the thermostat, low water levels or failure of motorised valves. It's a good idea to check if an issue with boiler pressure or your thermostat is causing the issue.

If you think that your boiler needs a new part then you'll need to get a Gas Safe registered engineer on the case. They'll be able to thoroughly diagnose the problem and replace any broken parts where necessary.

Radiators not heating up

If your radiators aren't heating up or are only heating up at the bottom there could be air trapped in the system. When there’s too much air, it can cause blockages, which will prevent the hot water from circulating around the radiators. To get the radiators heating up again, they may need to be bled.

How to bleed radiators

Before getting started with bleeding the radiators, make sure the central heating is turned off. Never bleed the radiators while the heating is on.

Once the heating is off and the system has had a chance to cool down, follow these steps to bleeding a radiator. Don’t hesitate to contact a Gas Safe registered engineer to take care of this if you don’t feel comfortable.

Heating but no hot water

ATAG combi boilers send hot water instantly to the radiators or hot water tap depending on which you need at the time. A diverter valve directs the water to the appropriate outlet but from time to time, especially on older boilers, they can get stuck, meaning that even though you’re turning the hot tap on, the radiators are getting warm.

Fixing a diverter valve

A diverter valve isn’t something you can fix yourself, you’ll need a professional heating engineer to either repair the diverter valve or replace it, depending on its condition.

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Which ATAG boiler problems need an engineer?

We've put together a list of the most common boiler symptoms, to give you an idea of what they might mean and whether you'll be able to fix it yourself or need an engineer.

Problem Possible cause Do you need an engineer?
No heat or hot water Broken diaphragms and airlocks, failure of motorised valves, issues with the thermostat or low water levels Yes
Leaking and dripping Most common cause is a broken internal component but it will depend on where the water is leaking from Yes
Banging, whistling or gurgling noises A common cause is air in the system, alternatively it could be that the water pressure is too low or it's kettling Yes
Pilot light goes out Could be a broken thermocouple which is stopping the gas supply Yes
Losing pressure Could be a water leak in the system, the pressure relief valve needs replacing or due to recently bleeding radiators No, unless there's a leak
Frozen condensate pipe Your boiler will often display a fault code or warning notification Yes
Thermostat issues Thermostat may be turned off or not set to the correct settings (time etc.) Consider replacing
Kettling Limescale or sludge building up on your boiler's heat exchanger Yes
Radiators not getting hot You will need to bleed the radiators which doesn't require an engineer unless you don't feel like carrying out the task yourself. Yes
Boiler keeps switching itself off Could be low water pressure, a problem with the thermostat or a lack of water flow due to a closed valve, air or the pump not circulating the water in the system properly Yes

ATAG boiler warranty

ATAG boilers come with 10 years warranty as standard, giving you peace of mind well after your boiler is installed. We've put together a complete guide to ATAG warranties so that you know exactly what to expect. One thing you’ll need to know when it comes to any boiler warranty, including ATAG boilers is that the unit must be serviced annually or the warranty will end early. Find out what a service involves by visiting our guide to ATAG boiler services.

Send us an enquiry today to receive free quotes for a new boiler and find trusted engineers near you with our free service.

Boiler insurance and ongoing cover

If your boiler warranty has expired, then boiler insurance is a possible option. You can take out insurance with your energy supplier but you're absolutely no obligation to do so. When comparing insurance, the best ones will include an annual service and safety inspection, so keep an eye out for them.

Is it time to replace your ATAG boiler?

If you've had your ATAG boiler for some period of time then it's worth considering a new one as you could be saving up to £365* a year in a detached home. Take a look at the table below to see how much you could be saving depending on your current boiler rating and property.

House Type G (< 70%) F (70-74%) E (74-78%) D (78-82%)
Semi-Detached £240 £170 £150 £135
Detached £365 £255 £205 £165
Detached Bungalow £190 £135 £120 £105
Mid Terrace House £205 £145 £130 £115
Flat (Mid Floor) £95 £65 £60 £50

Figures are for England, Scotland and Wales only*.

Who should replace an ATAG boiler?

If you think a new boiler is the right way to go then the next big decision is choosing who to replace it. The easy part is knowing that no matter who you get to replace a boiler they must be Gas Safe registered. Now that we've got that part out of the way, your choice ultimately comes down to a local engineer or a national company.

Local engineers can offer a very competitive rate and as they tend to be just one man and his van, you'll get a very personal service from the same person throughout your communications. It's always a good idea to get a quote from more than 1 engineer to make sure you're getting the best deal, we recommend getting up to 3.

While branded manufacturers may be slightly more on the expensive side, big brand protection is a huge bonus and they can provide extra service such as ongoing boiler cover.

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Data Source: Energy Saving Trust, Heating Your Home: Boilers (2022)
*Based on replacing an old gas boiler with a condensing A-rated boiler with thermostatic radiator valves, programmer and room thermostat in a detached home. Figures are based on fuel prices as of November 2021.

Rob Wells

About the author

Rob Wells

Rob is another of our resident home heating experts. He manages our external partnerships, making sure you get the most up to date information.

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