Atag Boiler Repairs

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Atag Boiler Repairs London

Gas Safe registered engineers • 24/7 call handling • London wide

Call Now: 0203 868 6251 | Request a Call Back

Tell us the fault code and model. We will advise the safest next step.

We cover ATAG boiler repairs in London, including lockouts, no heating, no hot water, low pressure, leaks and fault codes.

Quick Navigation

• Safety First
• Quick Checks Before You Call
• Fault Code Table
• Most Searched Problems
• Why Atag Boilers Fail
• Models We Repair
• Repair or Replace

Safety First

Smell gas? Turn off the gas supply at the meter if it is safe to do so. Open windows. Leave the property. Call the National Gas Emergency Service on 0800 111 999. Do not use switches, and do not use naked flames.

CO alarm sounding? Open windows immediately. Leave the property. Call 999. Do not re-enter until cleared by emergency services.

Boiler leaking heavily? Turn off the boiler at the controls. If safe, turn off the water supply. Call an engineer.

Quick Checks Before You Call

Before calling an engineer, these safe checks may resolve simple issues with your Atag boiler.

Check the gas supply
Is gas working at other appliances in your home? If not, check your meter and any prepayment credit.

Check the pressure gauge
Atag boilers show pressure on the digital display. It should read between 1 and 1.5 bar when cold. If below 1 bar, you may need to re pressurise using the filling loop.

Check the thermostat
Is the room thermostat set above current room temperature? Are the batteries working?

Check the timer or programmer
Is the heating scheduled to be on? Check the clock is set correctly.

Try a single reset
Locate the reset button on your Atag boiler. Press once and wait. If the fault returns, do not keep resetting. Call an engineer.

Check the condensate pipe
In cold weather, the external condensate pipe can freeze. Look for a white plastic pipe exiting through an outside wall. If frozen, pour warm water over it gently.

Atag Fault Codes Explained

ATAG boilers can show blocking codes (temporary) and error codes (lockout). Code formats vary by model range and display type, so read the code exactly as shown. The table below lists common ATAG A-Series examples. If your code is not listed, tell us exactly what appears on the display.

If you smell gas or suspect fumes, do not reset. Follow the Safety First steps above and call for help.

Need help now? Call 0203 868 6251 and tell us the code and model.

Most Searched Atag Problems

If you are seeing a lockout, loss of hot water, or your Atag boiler keeps resetting, tell us the fault code and model and we will confirm the safest next step.

C1 33 ignition lockout

C1 33 is one of the most common ATAG fault codes. It means the boiler tried to ignite but no flame was detected. Common causes include gas supply issues, a faulty ignition electrode, or a blocked condensate pipe in winter. Check gas is on elsewhere in the home. Try one reset. If C1 33 returns, stop and call an engineer for ATAG boiler repair.

C1 18 low pressure

C1 18 appears when system pressure drops below the minimum threshold. On ATAG boilers, you can re pressurise using the filling loop. If you top up and pressure falls again within days, there may be a leak in the system or a failing expansion vessel. Do not keep topping up. Call an engineer to find the cause.

No hot water but heating works

On ATAG combi boilers, you may get heating but no hot water. This often points to a diverter valve issue or a flow sensor fault. The diverter valve directs hot water between taps and radiators. When it wears or sticks, hot water delivery becomes unreliable. Call an engineer for diagnosis.

Why Atag Boilers Develop Faults

ATAG boilers are known for build quality and efficiency. Here is what we commonly see.

Ignition electrode wear

Ignition faults like C1 33 are common on ATAG boilers over 5 years old. The ignition electrode creates the spark, and over time it can wear or become coated with carbon. Condensate blockages in winter also contribute to repeated lockouts.

Pressure relief valve and expansion vessel

C1 18 and C 78 pressure faults often point to a failing expansion vessel or a weeping pressure relief valve. The expansion vessel absorbs pressure changes as water heats and cools. If the diaphragm fails or the air charge is lost, pressure drops occur frequently.

Diverter valve on combi boilers

The diverter valve directs hot water between your taps and radiators. When it wears or sticks, you may get heating but no hot water, or the reverse. This is common on ATAG combis over 8 years old.

PCB and electrical faults

The printed circuit board controls all boiler functions. On older ATAG models, PCB faults become more common after 10 years. Symptoms include erratic displays or random lockouts.

Atag Models We Repair

We repair ATAG combi, system, and regular boilers, including A-Series and iC models. If you can, tell us the model range and whether it is a combi or system boiler. We will confirm parts availability before booking where possible.

ATAG parts can be more specialist than mainstream UK brands. We check availability before attending and advise honestly if repair is not viable or cost effective.

Repair or Replace Your Atag Boiler?

We help you decide based on age, reliability, and parts availability.

Repair makes sense when

• Boiler is under 10 years old
• This is the first major fault
• Parts are readily available
• Boiler has been regularly serviced

Replacement may be better when

• Boiler is 12 to 15 years old or more
• You have had multiple breakdowns recently
• Parts are obsolete or hard to source
• The boiler is undersized for the property
• Energy bills are higher than expected for the property size

Our engineers give honest assessments. We focus on safety and reliability, not pushing unnecessary replacements.

Atag Boiler Servicing

Regular servicing reduces breakdown risk and keeps your ATAG boiler running efficiently. We recommend annual servicing for all ATAG boilers.

A service visit includes inspection of key components, combustion analysis where appropriate, pressure checks, and cleaning where needed. We provide written service records.

Landlords and Letting Agents

We provide boiler repairs and gas safety certification for landlords across London.

Gas Safety Certificates (CP12)
Annual gas safety checks are a legal requirement for rental properties. We issue CP12 certificates and can send documentation directly to managing agents.

Repair and compliance
We can invoice agents directly and provide records for compliance files.

Atag Repairs Across London

London wide coverage for ATAG boiler repairs. Book an engineer or view our London areas page.

Other Boiler Brands We Repair

Worcester • Vaillant • Ideal • Baxi • Glow worm • Viessmann • Potterton • Vokera • Alpha • Ferroli

View all brands

Atag Boiler Repair FAQs

How quickly can you attend for an Atag breakdown?

We offer same day attendance where slots are available. For no heating or hot water, we prioritise urgent breakdowns. Call our 24/7 line and we will advise availability.

Do you carry Atag parts?

ATAG parts can be more specialist than mainstream UK brands. We check availability and source parts as quickly as possible. For common faults, we often have compatible components available.

Is it safe to reset my Atag boiler after a fault code?

A single reset is generally safe. If the fault returns after resetting, stop and call an engineer. Do not reset more than twice in 24 hours. If you smell gas or suspect fumes, do not reset.

How much does an Atag boiler repair cost?

Costs vary depending on the fault and parts required. We diagnose first and quote before any repair work begins.

Speak to Our Team

For safe next steps, call now or request a call back.

Call 0203 868 6251 | Book an Engineer

Gas Safe registered • 24/7 call handling • Quote before work