The ecoFIT pure 825–835 operating instructions specify a cold-system filling pressure of 1.0–2.0 bar. The filling arrangement and the pressure needed for your property must be confirmed before you add water.
Which ecoFIT pure and which pressure?
This guide uses Vaillant’s operator instructions for ecoFIT pure 825–835, document 0020230532_03. It is not a filling procedure for every ecoFIT model. Read your matching manual and the installer’s handover advice first.
The stated 1.0–2.0 bar range is for a cold heating system. Vaillant notes that a higher pressure may be needed for a building with several storeys; the installer should advise. Do not automatically aim for the top of the range or use the hot reading as a cold filling target.
What does F.22 tell you?
In these instructions, F.22 can indicate that the system pressure is too low. Read the pressure display and record the full message. The code does not explain why the pressure fell and is not permission to keep adding water.
If the pressure is already appropriate, the code persists, or water is leaking, ask a competent engineer to investigate. For a repeated pattern, see boiler pressure that keeps dropping.
Before topping up: identify the correct filling device
Vaillant’s instructions tell the user to have a competent person explain where the filling device is and how it is used. Do not guess which valves beneath a boiler to open. A generic internet video may show a different installation.
- Let the heating cool, read the pressure and check your exact operator manual.
- Confirm the filling device and the pressure recommended for your installation with your installer.
- Only if you understand the permitted procedure, follow that manual while watching the display. Close the controls and complete any disconnection exactly as instructed.
- Check the final reading. Stop and get help if pressure cannot be controlled, the method is unclear or the fault returns.
Do not open the appliance casing, operate unfamiliar components or attempt internal repairs. Repeated replenishment needs investigation.
What to send with a pressure-loss enquiry
Tell us the exact model, the cold reading, whether it changes markedly when hot, the full fault code and when it was last topped up. Photos of the display and safely accessible damp areas can help prepare the visit.
SwiftHeat UK Group Ltd offers an initial boiler diagnostic visit for £85 including VAT in Cardiff and South Wales, subject to availability. Parts and further repair work are quoted separately. Tell us your postcode, make, model, full fault code and whether heating, hot water or both are affected. If you rent, report the fault to your landlord or managing agent first.
See our boiler diagnosis and repair service. A fault code does not by itself establish that a boiler needs replacing.
For new-installation research, our ecoFIT pure combi model guide explains outputs and qualified warranty options.
Gas and carbon-monoxide concerns
If you smell gas, suspect a gas leak or a carbon-monoxide alarm sounds, stop troubleshooting and leave the building. For a suspected mains-gas emergency in Great Britain, call 0800 111 999 from a safe place outside. For LPG, contact the emergency number supplied by your LPG provider. Do not operate electrical switches or use flames. Never remove the boiler casing or attempt work on gas, combustion or electrical components.
Manufacturer guidance and further reading
Published by SwiftHeat UK Group Ltd using the manufacturer resources below, consulted on 28 October 2026. Follow the user manual for your exact appliance; this guide does not replace an on-site diagnosis. About our heating guidance and how to raise a correction.
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Discuss pressure loss or a boiler fault
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Tell us what you have noticed and your postcode. We will explain the appropriate assessment; submitting an enquiry does not confirm an appointment.
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