- Boilers
- Gas boiler
E118
Baxi E118 on a gas boiler: water pressure too low
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Baxi E118 means the pressure in the heating circuit is too low. With the boiler cold, read the gauge: if it shows under 1 bar, top up with the filling tap to 1 to 1.5 bar and bleed the radiators.
Safety first
Stop and check this first
- Do not raise the pressure above what Baxi asks: code 117 warns of pressure that is too high (over 2.7 bar). If pressure drops often, Baxi says to call the service centre instead of topping up again.
- If you smell gas: switch the boiler off, do not operate any electrical device or switch on lights, put out any flame, open the windows and leave; from outside, call your gas distributor's emergency number and the service centre. If you smell combustion fumes, switch the boiler off, ventilate and call the service centre.
Safe checks you can perform
- Pressure on the gauge
- Visible leaks and safety valve outlet
- Technician check of the pressure loss
Leave these tasks to a qualified professional
- Do not attempt this professional task: Hydraulic pressure switch check
- Do not attempt this professional task: Pressure and expansion vessel test
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Hydraulic pressure switch check
What they doIf pressure is correct and 118 remains, the technician checks the pressure switch and its wiring.
They must show youthe gauge reading against the boiler's warning.
In writingthe part number replaced and why.
Pressure and expansion vessel test
What they doThe technician checks with the boiler idle whether the system loses pressure and measures the expansion vessel pre-charge.
They must show youthe pressure at the start and end of the test.
In writingwhere the loss was and what was repaired.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Pressure on the gauge
- Who:
- you.
- How:
- with the system cold, read the boiler pressure gauge. Baxi asks for 1 to 1.5 bar when cold. Do not open the casing.
- Result that matters:
- whether the needle sits between 1 and 1.5 bar or below it.
- If it is below 1 bar:
- Baxi says to top up slowly with the boiler filling tap and then bleed the radiators; then see whether 118 comes back.
- If the pressure is correct:
- lack of water does not explain the code; do not add more.
- Evidence to keep:
- a dated photo of the gauge and a note each time you have to top up.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
Visible leaks and safety valve outlet
- Who:
- you.
- How:
- look under radiators, valves and the boiler without taking anything apart. Baxi notes the safety valve discharge must go to a visible, unblocked point.
- Result that matters:
- whether there is water, staining or a drip at the safety valve outlet.
- If you see water or a drip:
- there is a real loss; do not keep topping up and call the service centre.
- If everything is dry and pressure holds after topping up:
- it points to a one-off loss, not a fault.
- Evidence to keep:
- photos of any staining or drip and the date.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
Technician check of the pressure loss
- Who:
- official service technician or registered company.
- How:
- checks the expansion vessel, the safety valve and the hydraulic pressure switch, and looks for the leak in the system.
- Result that matters:
- whether pressure drops with the boiler idle and where the water goes.
- If they find a leak or a discharging valve:
- that confirms the cause of 118.
- If pressure holds and the code remains:
- it points to the pressure switch or its connection.
- Evidence to keep:
- a report with what was checked, the measured pressure and any part replaced.
Opening the boiler and working on the internal water circuit is for the technician; you only use the external filling tap.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Baxi
- Product type
- Gas boiler
Known code variants
- 118
- Baxi 118
- Baxi E 118
- Error 118 Baxi
- Platinum Compact 118
What it means
In the Platinum Compact ECO fault table, code 118 is pressure too low in the hydraulic circuit. The boiler has a hydraulic pressure switch that stops it running without water. Pressure can drop from a leak in radiators or pipes, from the safety valve discharging or from air bled out; if it keeps dropping, Baxi says to call the service centre. The code measures pressure, it does not find the leak.
Warnings and stop conditions
- Mediumsource verified
Do not raise the pressure above what Baxi asks: code 117 warns of pressure that is too high (over 2.7 bar). If pressure drops often, Baxi says to call the service centre instead of topping up again.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
- Criticalsource verified
If you smell gas: switch the boiler off, do not operate any electrical device or switch on lights, put out any flame, open the windows and leave; from outside, call your gas distributor's emergency number and the service centre. If you smell combustion fumes, switch the boiler off, ventilate and call the service centre.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
Symptoms and causes
Probable causes · in order
- Low pressure after bleeding or over timeCommon
A slow loss is normal after bleeding radiators. If the top up holds for weeks, that was it and not a fault.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
- Leak in the system or safety valve dischargePossible
If you top up every few days, water is escaping somewhere: marks under radiators or a drip at the safety valve outlet.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
- Pressure switch or pressure readingPossible
If the gauge reads correctly and 118 remains, the fault may be in the pressure switch or its wiring; only the technician can tell.
Evidence: Baxi Platinum Compact ECO, instrucciones de funcionamiento y mantenimiento para el usuario
Virtual technician
Does E118 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
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