Boiler showing a fault code, or a radiator that will not heat up? These guides explain what is actually happening, what you can safely sort out yourself, and the point at which it needs a Gas Safe engineer. We give away the easy fixes because most of them genuinely are easy.

Start here

• Boiler not firing up, work through this one first
• Boiler keeps losing pressure
• Radiator not heating up
• No hot water but heating works
• Boiler making a banging noise
• Frozen condensate pipe

Vaillant fault codes

Vantage is a Vaillant accredited installer.

• F22, low pressure. You can usually fix this yourself.
• F75, pump or pressure sensor.
• F28, ignition failure.
• F29, flame lost during operation.
• F27, flame detected when there should be none.
• F20, overheat cut-out.
• F23, flow and return difference too great.
• F83, no temperature rise at start-up.
• F32, fan fault.
• F62, gas valve shut-off delay.
• F61, gas valve control fault.
• F72, flow or return sensor fault.

Ideal fault codes

• F1, low pressure. You can usually fix this yourself.
• L2, ignition lockout, including Logic, Vogue and Independent.
• F2, flame loss.
• F3, fan fault.

Baxi and Potterton

• Baxi E133, ignition lockout.
• Baxi E110, overheat.
• Baxi E125, circulation fault.
• Baxi and Potterton E119, low pressure.

Glow-worm, Viessmann and Worcester Bosch

• Glow-worm F28, ignition failure.
• Glow-worm F22, low pressure.
• Viessmann F4, flame failure.
• Worcester Bosch codes, EA, 227, E9, U9, A21 and C6 explained.
• Worcester Bosch EA 227, the most common lockout and how to clear it.

How-to guides

• How to bleed a radiator
• How to fix a running toilet
• How to unblock a shower drain

Choosing and replacing

• Best combi boilers, an installer view
• How long does a boiler last?
• Boiler cover compared

When it needs an engineer

We are Gas Safe registered and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day.

• Boiler repair
• Boiler servicing
• Power flushing
• Emergency plumbing
• Leak detection

Worcester Bosch fault codes explained in full

We have written up each of these individually, with what the code officially means, what you can safely check yourself and when it needs a Gas Safe engineer.

• Worcester Bosch EA – flame not detected during operation
• Worcester Bosch A1 – pump has run dry
• Worcester Bosch E9 – safety temperature circuit tripped
• Worcester Bosch C6 – fan speed too low
• Worcester Bosch E2 – flow temperature sensor defective
• Worcester Bosch F0 – internal failure
• Worcester Bosch F7 – flame still detected after shutdown
• Worcester Bosch FA – flame detected after the appliance switches off
• Worcester Bosch Fd – reset button pressed inadvertently

Definitions taken from the Worcester Bosch Greenstar CDi Classic engineer’s service booklet. Codes vary between models and generations, so if yours behaves differently, check the manual for your appliance or ring us on 01462 506374.

Problem guides: what a plumber actually checks

Walkthroughs of the faults we get called to most, in the order an engineer works through them.

• Low water pressure through the whole house
• Banging or knocking pipes
• Shower running hot and cold
• Drain smell inside the house
• Toilet keeps blocking again and again

Ideal fault codes explained

Definitions taken from the Ideal installation and servicing guide, Section 4 Fault Finding.

• Ideal F1 – low water pressure
• Ideal F2 – flame loss
• Ideal F3 – fan fault
• Ideal F4 or L4 – flow thermistor fault
• Ideal F5 or L5 – return thermistor fault
• Ideal F6 – outside sensor fault
• Ideal F7 – low mains voltage
• Ideal F8 or L8 – parameter or gas valve fault
• Ideal F9 or L9 – PCB fault
• Ideal L1 – flow temperature overheat lockout
• Ideal L2 – ignition lockout
• Ideal L6 – false flame lockout
• Ideal LC – five resets within fifteen minutes

Codes vary across the Ideal range. If yours behaves differently, check the manual for your appliance or ring us on 01462 506374.

Baxi fault codes explained

Definitions taken from the official Baxi error code table.

• Baxi E09 – gas valve connection fault
• Baxi E10 – external probe fault
• Baxi E20 – central heating sensor fault
• Baxi E28 – flue sensor fault
• Baxi E110 – overheat cut-out
• Baxi / Potterton E119 – low water pressure
• Baxi E125 – water circulation fault
• Baxi E128 – frequent loss of flame
• Baxi E133 – gas supply fault
• Baxi E160 – fan fault
• Baxi E.04.10 – burner failed to ignite

Newer Baxi appliances use the dotted code format. If yours differs, ring us on 01462 506374.

Glow-worm fault codes explained

Definitions taken from the Glow-worm Energy range fault finding table. Glow-worm is part of the Vaillant Group and shares much of its code structure with Vaillant.

• Glow-worm F.20 – overheating safety switch-off
• Glow-worm F.22 – low water pressure
• Glow-worm F.23 – temperature difference too great
• Glow-worm F.24 – temperature rise too fast
• Glow-worm F.25 – flue gas temperature too high
• Glow-worm F.27 – fault in flame detection
• Glow-worm F.28 – ignition unsuccessful
• Glow-worm F.29 – flame loss
• Glow-worm F.32 – fan speed fault
• Glow-worm F.61 – gas valve control fault
• Glow-worm F.75 – pressure sensor fault

If your Glow-worm is from a different range and the code behaves differently, ring us on 01462 506374.