E1 Boiler Error Code: What It Means & How to Fix It

An E1 on a boiler is usually the first half of a three-digit code on Baxi, Potterton and Main boilers. The display shows E1, then two more digits, so E119 means low pressure, and E133 means the boiler can’t light. Those last two digits tell you whether you can fix it yourself.

A boiler flashing E1 has only given you half the code. Topping up the pressure through the filling loop clears E119, but it won’t help with E133, and E160, a fan fault, needs an engineer. Reading the full E1 error code first saves a reset that won’t work and sometimes a call-out. The sections below cover the codes you’re likely to see, how to top up the pressure, and when to call a Gas Safe registered engineer.

What does E1 mean on a boiler?

On Baxi, Potterton and Main boilers, the E1 error code is split across the display. E1 shows, pauses, then the last two digits appear, and the pause is easy to miss. Wait for the second half and write both parts down, because E1 alone could be low pressure, a gas fault or a fan fault; then find your code in the table.

What does an E1 error mean on a Baxi boiler?

A Baxi boiler E1 error code is usually E119 or E133. Check the pressure gauge; if it reads below 1 bar, the code is E119 (low pressure). If the pressure is normal, look at the display for E133 or another code in the table above.

The same codes appear on Baxi combi boilers across the Duo-tec, EcoBlue and 400, 600 and 800 ranges, so go by the digits, not the model. Your manual lists every code the boiler can show, and F-codes are covered under Baxi boiler error codes.

What does an E1 error mean on a Potterton or Main boiler?

A Potterton boiler E1 error is the same as a Baxi boiler E1 error, because both brands belong to the Baxi Heating UK group. E119 and E133 mean the same on all three brands, including the Promax, so the table above applies to each. The only difference is that some Potterton models, such as the Assure, show E118 for low pressure

Any other Potterton E1 fault is listed under Potterton boiler fault codes, and Main publishes its own list for a Main boiler E1 error.

Does E1 mean the same on other boiler brands?

No, other brands have different low-pressure codes. Both Vaillant and Glow-worm display F22 for low pressure. F1 is used in the Ideal Logic models; the other Ideal boiler fault codes follow their own pattern, while Worcester Bosch doesn’t use low pressure as fault E1.

How do you fix an E1 boiler error caused by low pressure?

To fix an E1 error on a Baxi boiler showing E119, repressurise it to 1 to 1.5 bar and reset. This only requires a few steps, while the casing stays on.

Step 1: Check the Pressure Gauge:

Check the pressure gauge with the boiler cold. If the reading is less than 1 bar, this indicates that there is low water pressure.

Step 2: Find the Filling Loop:

Look for a boiler filling loop underneath. These are mostly external braided hoses that have one or two taps or levers, which open when turned in line with the pipe. Some of the Baxi and Potterton models have a built-in loop that works with a key or wheel valve instead.

Step 3: Top Up the Pressure:

To increase the boiler pressure, open the loop slowly and watch the gauge, because the needle lags and it’s easy to overshoot. Close the valve once it reads 1 to 1.5 bar.

Step 4: Reset the Boiler:

On dial models, move the dial knob to the left to reset and hold for 5-15 seconds as per manual instructions.

Step 5: Check for Leaks:

Check pipes, radiators and valves for leaks, and re-check the gauge in a couple of hours.

Step 6: Release Excess Water:

If the needle is past the green zone, it is an indication of excess water. Leave it and ask an engineer how to release it safely.

What does E133 mean on a boiler and how do you fix it?

E133 indicates that the boiler attempted to light and failed to do so. Make sure the gas is turned on and, if you have a prepay meter, check that it has credit. When the weather is cold, the condensate pipe can freeze and show the same code, so first thaw the frozen condensate pipe, then reset it once, and call an engineer if the code reappears.

E1 on your boiler but the pressure is fine?

If the pressure is between 1 and 1.5 bar and the E1 code is visible on the boiler, then it is not the pressure; check the numbers with the table for E133, E110, E125, E160 or E168. Note the exact digits and any code before resetting, as E168 can replace the original fault on the display.

Why does an E1 boiler fault keep coming back?

If an E1 boiler fault occurs after a top-up, then there is a leak somewhere in the system. Most cases are due to slow leaks at a pipe, joint, or valve, and bleeding the radiators will relieve air and reduce the pressure. The needle swings up and down due to a dropping pressure from a failed expansion vessel, and a relief valve which has opened drips from its discharge pipe outside.

If the boiler pressure keeps dropping, work through those first. When none of them turns anything up, the relief valve and expansion vessel are the next places to look on a boiler losing pressure but no leaks.

When to call a Gas Safe engineer

Call a Gas Safe registered engineer straight away if:

• the code is E125, E130 or E160
• E110, E133 or E168 comes back after one reset
• the pressure drops again within a few days
• water comes out of the pressure relief valve pipe

If you smell gas, leave the property and call the National Gas Emergency Service on 0800 111 999 first. Never take the boiler casing off. To get the fault found and fixed, book a boiler repair.

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How can you prevent E1 boiler faults?

A boiler service once a year identifies all pressure loss and worn-down parts before they stop the boiler. Check the gauge between services at least once per month in winter, lag the condensate pipe when exposed to the outside air, and bleed radiators only when there are cold spots; check the gauge afterwards. Catching leaks early is key, as a slow drip is a common cause of a repeat E1 fault code.

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What should you do when your boiler shows E1?

Note down both parts of the code before you touch anything. Digits 19 mean low pressure, which you can top up yourself. Any other E1 error code needs a Gas Safe registered engineer, with one reset first for E110, E133 and E168, and the exact digits and any earlier code so they arrive with the right part.

24|7 Home Rescue fixes the cause when E1 keeps returning. A Gas Safe registered engineer finds the fault and repairs it, with parts, labour and VAT included in the price. Ring the helpline about any boiler fault, and add boiler cover to be protected if it breaks down again.

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