Vaillant 981158 Packing Rings

The Vaillant 981158 is a replacement O-ring, supplied as a single item. It is a soft, circular seal that sits in a machined groove or joint face inside Vaillant water heaters, compressing between two mating surfaces to stop water escaping past the connection it serves. Because it is a compression seal rather than a mechanical component, it is treated as a wear item: it is normally renewed whenever the joint is opened, and always when a weep or drip appears at that point.

• Water weeping or a visible drip at the joint the O-ring seals
• Limescale or mineral deposits built up around the seal groove or joint face
• The ring feels hard, flattened or brittle instead of pliable when handled
• Cracks, nicks or a squared-off cross-section visible once the ring is removed
• Repeated pressure loss at a connection that has already been tightened once

• Check part number 981158 against the appliance's parts list or data plate before ordering
• Confirm the ring's internal diameter, cross-section and material suit the groove it sits in
• If the same joint also uses a gasket, fibre washer or lip seal, order those at the same time
• Isolate and drain the appliance before opening any water-carrying joint, and follow the manufacturer's service procedure