Vaillant Venturi VAILLANT0020135123

The Vaillant 0020135123 is a venturi, a shaped restriction that sits in the air or gas pathway of a Vaillant appliance and governs how the flow behaves as it passes through. By narrowing the bore, it produces a controlled pressure drop that the appliance's control system uses to regulate combustion and hold a steady output. It is supplied by Vaillant as a service component for repair and maintenance work on standard water heaters, and it is normally replaced when the original has become blocked, damaged or worn rather than as part of routine servicing.

• Combustion that will not hold steady, with the appliance hunting or modulating erratically
• Repeated lockouts or fault codes relating to air or gas flow
• Soot deposits, discolouration or localised overheating around the burner area
• Whistling, popping or other unusual noise from the air and gas pathway
• Visible blockage, corrosion or mechanical damage at the venturi when the appliance is opened up

• Confirm the part number 0020135123 against the appliance data plate and against the component being removed.
• Check the appliance model and serial number so the correct variant is ordered.
• Inspect any seals, gaskets or O-rings on the air and gas pathway and renew them if they are disturbed during the repair.
• Keep the old component to hand until the replacement is fitted and the appliance has been checked through.