Medium
S.85 on Vaillant Atmomax

Your boiler is struggling to move enough water through the system, usually due to a blockage, air bubbles, or a problem with the pump.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Service message quantity of circulation water

DIY fix possible

Check that all radiator valves are fully openBleed all radiators to remove trapped airEnsure the boiler pressure is topped up to between 1 and 1.5 bar

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Related fault codes

F.22View →F.24View →S.53View →

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