Ariston Boiler Repairs London

Ariston Boiler Repair Help Centre

Common Ariston faults, fault codes, safe checks, and when to call a Gas Safe engineer.

We specialise in Ariston boiler repairs across London.

Gas Safe registered engineers for safe diagnosis, repair and testing.

24/7 availability with London wide call handling and booking.

Jump to: Fault Codes · 501 Ignition · Pressure · Frozen Condensate · Repair or Replace

Quick Checks Before You Call Anyone

These take 60 seconds and solve a surprising number of lockouts:

1. Check the pressure gauge: If below 1 bar, top up to 1.0 to 1.5 bar. Use our complete pressure guide.
2. Note the fault code: Ariston boilers often show 3 digit codes like 501 or 108. Write it down before calling.
3. Check your fuse box: Boilers need electricity, a tripped switch is an easy fix.
4. Check thermostat and timer: Settings can change after power cuts or dead batteries.
5. Freezing weather? The condensate pipe may be frozen (see winter section below).
6. Reset once only: Use the reset button on the front panel once, then wait 60 seconds. If it locks out again, stop and call an engineer.

Ariston Fault Codes

Note: Ariston fault codes can vary by model and generation. If your code is not listed, call us with the exact code and model and we will advise the safest next step.

501: Ignition Failure

What is happening: The boiler is trying to light but cannot establish a stable flame.

Common causes: Gas supply interruption, frozen condensate pipe (winter), ignition components, airflow or flue issues, gas valve or PCB related faults.

What to try: Check your gas hob or other gas appliances work. In freezing weather, check the condensate pipe for ice. Reset once only. If the boiler will not ignite, call an engineer.

108: Low Water Pressure

What is happening: System pressure has dropped below the minimum operating level and the boiler may lock out to protect itself.

Common causes: Recently bled radiators, a small leak, pressure relief discharge, or the expansion vessel needing attention.

What to try: Top up using the filling loop and aim for 1.0 to 1.5 bar. If you need to top up frequently, there is likely a leak or a component issue. Use our pressure guide.

How to Top Up Pressure (Ariston)

If you are not comfortable using the filling loop, stop and call a Gas Safe engineer.

Do not remove the boiler casing. If you cannot locate the filling loop easily, call an engineer.

1. Locate the filling loop (often underneath the boiler, a braided silver hose with one or two valves).
2. Ensure the boiler is off and cool.
3. Open the valves slowly, a quarter turn at a time.
4. Watch the pressure rise to between 1.0 and 1.5 bar.
5. Close both valves fully.
6. Switch the boiler back on.

Do not exceed 2.0 bar. If you overfill, stop and call an engineer.

Frozen Condensate Pipe (Winter)

In freezing weather, a frozen condensate pipe is a common cause of ignition related lockouts on condensing boilers. This is often safe to resolve with the steps below. If you are unsure, or the boiler will not restart, call an engineer.

Signs: Lockout during freezing temperatures, gurgling when the boiler tries to start, repeated ignition failures such as 501.

What to do:

1. Locate the condensate pipe (white or grey plastic pipe running to an outside drain).
2. Pour warm water (not boiling) over the frozen section.
3. Reset the boiler once thawed.

Full instructions: Frozen condensate pipe guide.

Why These Faults Are Common in London Homes

Hard water, older pipework, and winter weather make certain faults more likely in London properties:

• Ignition lockouts: Winter condensate freezing can trigger repeated ignition failures.
• Circulation issues: Sludge and limescale can restrict flow, leading to circulation and overheating faults.
• Pressure drops: Older systems can lose pressure after radiator bleeding or due to small leaks.
• Noise and kettling: Scale can cause kettling and overheating. See our guide to boiler noises.

Ariston Models We Repair

We repair Ariston boiler models including:

• Clas: Widely installed combi range
• Genus: Higher specification combi and system range
• Alteas: Premium range on some installations
• E-Combi: Compact combi models
• System and heat only: Ariston system boilers and heat only boilers in older properties

Common Ariston Problems

Ignition failures (501): Repeated failed ignition attempts linked to gas supply, condensate freezing, ignition components, or airflow issues.

Low pressure (108): Often after bleeding radiators or due to a small system leak.

Circulation faults (103): Poor flow due to sludge, a tired pump, airlocks, or restricted pipework.

Fan and flue faults (607): Fan not proving correctly or airflow issues that need safe testing.

Diverter valve issues: Hot water works but radiators stay cold, or vice versa, more common on older combis.

Repair or Replace?

Ariston boilers typically last 10 to 15 years with proper maintenance. If yours is approaching that age and needs a major repair (PCB, fan assembly, heat exchanger), replacement may be more cost effective.

We give honest advice either way. Read more: Repair or replace? An engineer’s guide.

If you decide on a new boiler: New boiler installation.

Ariston Servicing

Annual servicing helps keep your Ariston running safely and efficiently. We service Ariston models and provide a clear report after each visit.

We recommend servicing in late summer or early autumn, before the heating season. Book your boiler service.

Renting? Landlords: Check This

Tenants: Your landlord is usually responsible for boiler repairs. Contact them first and keep written records, especially if you have no heating or hot water.

Landlords: Stay compliant with our Gas Safety Certificate (CP12) service. See our full London landlord checklist covering gas safety, EPCs, and boiler maintenance.

London Wide Coverage

We repair Ariston boilers across all London boroughs. See our London coverage area or find your local page:

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