Baxi E133 fault code — what it means and how to fix it

What does the Baxi E133 fault code mean?

The Baxi E133 fault code means a gas supply fault — the boiler tried to light, couldn't detect a flame, and locked out to stay safe. In winter the usual cause is a frozen condensate pipe, which you can safely thaw yourself. If your gas is on and the pipe isn't frozen, E133 needs a Gas Safe registered engineer.

In plain terms, the boiler went to fire up, the flame either never caught or wasn't sensed, so it shut itself off rather than let gas keep flowing. Baxi's own guidance is to check the power supply, the sensing electrode, the spark electrode and the cable — but the last three of those are inside the boiler and are an engineer's job, not a homeowner's.

E133 shows up across the Baxi combi range, including the 600 and 800 series and the Duo-tec models. Baxi lists it in its own homeowner FAQ alongside codes like E119 and E128 as one of the common ones to understand.

Good news first: on its own, E133 is not a gas emergency. It usually points to something simple like a frozen condensate pipe or a gas supply that's been interrupted. The National Gas Emergency Service line, 0800 111 999, is only for when you can smell gas or your carbon monoxide alarm is going off — not for this code.

Key facts

The quick version, before we get into the detail.

• What it means: a gas supply fault — no flame detected, so the boiler locks out to stay safe.
• Most common winter cause: a frozen condensate pipe, which you can safely thaw yourself for nothing.
• DIY-fixable? Partly — thaw the condensate pipe, check the gas and any prepay meter, and reset once.
• Gas Safe job if: E133 returns after one reset, or the condensate pipe isn't frozen.
• Gas emergency? Call 0800 111 999 only if you can smell gas or your CO alarm sounds.
• Smart Plan boiler cover: parts and labour up to £500 (boiler under 7 years) or up to £200 (over 7 years). A £95 call-out fee can apply — check the plan terms so you know when.

Why does the Baxi E133 code appear?

E133 is triggered by anything that stops a flame forming or being sensed. There are four common culprits, roughly most-likely first: a frozen or blocked condensate pipe (the number-one winter cause), an interrupted or low gas supply (including a prepay meter that's run out of credit), a worn or dirty ignition or sensing electrode, and a gas valve fault.

The pattern matters. A reset clears the lockout but it doesn't fix anything. If E133 comes straight back after you reset — or clears and then returns when the boiler works harder — that's usually a sign of a developing fault, not a one-off glitch. Repeated resetting only masks it, and on a persistent lockout it can add wear to the ignition parts. Reset once. If it returns, stop and book a Gas Safe registered engineer.

Baxi E133 causes at a glance

How do I fix the Baxi E133 fault myself?

There are a few safe checks you can try before calling anyone out. None of them involve opening the boiler or touching anything to do with gas — that's the line you never cross. Work through them in this order.

1. Check your other gas appliances. If the hob or gas fire won't work either, it's a gas supply issue rather than the boiler itself.

2. Check the gas is on. Make sure the gas isn't switched off at the meter, and if you're on a prepay meter, check it has credit.

3. In cold weather, thaw the condensate pipe. Find the white plastic pipe running from the boiler out through an external wall. Pour warm — never boiling — water along the frozen section, or wrap it in a warm cloth or hot water bottle. Boiling water can crack the plastic.

4. Reset the boiler once. Follow the reset step in your Baxi manual. If E133 clears and stays clear, you're sorted — and a frozen-pipe thaw you do yourself costs nothing.

Reset once — and only once. If E133 comes back within minutes or hours, don't keep resetting it. That's the boiler telling you something is genuinely wrong, and repeated resets can add wear to the ignition parts. Stop there and book a Gas Safe registered engineer. To stop a condensate pipe refreezing in future, lag or insulate the outside section once it's thawed.

When should you call a Gas Safe registered engineer for E133?

Call an engineer if E133 returns after one reset, if your condensate pipe isn't frozen (or keeps refreezing), or if your other gas appliances work fine but the boiler still won't light. The ignition and sensing electrodes, the gas valve and the internal wiring are all engineer-only — it is illegal for anyone who isn't Gas Safe registered to work on the gas side of a boiler, and it isn't worth the risk. You can check an engineer is registered on the Gas Safe Register.

Repair costs depend entirely on the cause, so the honest answer is that it varies. A frozen-pipe thaw can cost nothing if you do it yourself, while an electrode, a gas valve or a control board is a bigger job. A Gas Safe registered engineer can diagnose it properly and tell you what's involved before any work starts.

If you'd rather not face a surprise repair bill when a fault does need an engineer, Smart Plan is a service plan, not insurance. It's modular, so you pick only the modules you want. A boiler module covers parts and labour up to your cover limit: up to £500 per 12-month period if your boiler is under 7 years old, or up to £200 if it's older. Worth knowing before you sign up: a £95 call-out fee can apply (check the plan terms for when), call-outs are Mon–Fri 08:00–18:00 unless it's a genuine emergency, and once you use a service a 12-month agreement period begins. Smart Plan is provided by UK Boiler Company Ltd, trading since 2014. And bear in mind that many E133s — a frozen condensate pipe most of all — you can often clear yourself for nothing, as above; cover is there for the faults that genuinely need an engineer, not the ones you can safely sort in a few minutes.

To book a one-off repair or set up cover, call 0333 772 6247 (Mon–Fri 08:00–18:00) and one of our Gas Safe registered engineers can come and fix it for you. Remember: 0800 111 999 is only for a gas smell or a CO alarm.

Baxi E133 fault code FAQs

Seeing E133? Get it repaired, or set up cover for next time.

Book a one-off repair and a Gas Safe registered engineer will sort it, or set up an ongoing Smart Plan boiler module so a future fault that does need an engineer is covered. Smart Plan is a service plan, not insurance: parts and labour up to your cover limit (£500 under 7 years, £200 over), a £95 call-out fee can apply, call-outs are Mon–Fri 08:00–18:00, and once you use a service a 12-month agreement period begins. Call 0333 772 6247.

Helpful links

• Baxi E119 low pressure fault
• Baxi E110 overheat fault
• All Baxi fault codes
• No heating? Book a repair
• Boiler & central heating cover
• Check an engineer on the Gas Safe Register
• Baxi official error code list