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Baxi Boiler E118 Error Code

Low water pressure in the heating circuit on Baxi boilers.

BaxiAll Baxi boiler codes

E118
Easy DIY fix

Pressure in the sealed heating circuit has dropped below the level the boiler will run at. The Combi 825 manual expects 1.0 to 2.5 bar and shows E118 when the reading is under 1.0 bar. Baxi blames low pressure on air in the system, a leak, an expansion vessel that needs recharging, or debris in the pressure relief valve.

Compatible models

Described in the Combi 825 user manual as pressure below 1.0 bar; 118 also appears in the Baxi 124 and Duo-tec 2 Combi GA error tables.

Also shown as

The older Platinum Combi shows low pressure as E119 instead.

Difficulty

Most people can clear this one at home with simple checks.

Not sure you are reading the code right? See how to read Baxi boiler codes.

Safety first: never take the casing off a gas boiler. If you smell gas, open windows, don't use light switches, turn the gas off at the meter if you can and call your gas emergency number from outside. A carbon monoxide alarm going off means the same: switch the boiler off, get fresh air and call.

How to fix Baxi E118

  1. Read the gauge

    Baxi's help pages give 1 to 2 bar as normal. A reading under 1 bar with E118 showing means the system needs water.

  2. Top up through the filling loop

    Repressurize exactly as your user guide shows; Baxi asks you to watch its repressurizing video before you start. Stop at about 1.5 bar and close the loop fully afterwards, because a loop left open keeps pushing the pressure up.

  3. Reset and recheck

    Clear the code with the reset button and note the reading. Look again the next morning and over the following week.

  4. Look for a leak

    Check radiators, valves and visible pipework for rust, staining or damp patches. A wet end on the pipe from the pressure relief valve outside means water is being let out.

When to call a technician

Pressure that keeps dropping needs an engineer. Baxi says recharging the expansion vessel and cleaning or replacing the relief valve are Gas Safe engineer jobs.

Parts linked to E118

These are the parts an engineer usually checks for this code. They sit inside the sealed casing, so leave them to a Gas Safe registered engineer.

Frequently asked questions

Which Baxi models show the E118 code?

Described in the Combi 825 user manual as pressure below 1.0 bar; 118 also appears in the Baxi 124 and Duo-tec 2 Combi GA error tables.

Can I fix Baxi E118 myself?

Usually, yes. Most E118 problems clear with simple checks you can do at home. Start with the first step above: read the gauge.

Other Baxi boiler codes

Last reviewed 2026-10-21. Codes and steps can vary by model; check your owner's manual.

Sources we checked