Vaillant 178969 Gasket, type C, (x10)

This is a Vaillant Type C gasket, supplied in a pack of ten under part number 178969. It is a sealing component used at a joint face on Vaillant heating and hot water appliances, where it compresses between mating surfaces to stop water or flue gases escaping. The gasket is a consumable item: it is replaced whenever the joint it seals is broken and remade.

• A weep or drip at the joint the gasket seals, often showing as a crusty white or green deposit around the flange or union.
• Water staining or damp patches beneath the appliance where the joint has been slowly seeping.
• The gasket is visibly flattened, hardened, cracked or perished when the joint is opened.
• The gasket has swollen or deformed, so the joint faces no longer sit square.
• A joint that has been disturbed during servicing and cannot be re-sealed reliably with the old gasket.

• Check the part number on your appliance's parts list or exploded diagram matches 178969, as gasket types are not interchangeable across joints.
• Confirm the joint you are working on takes a Type C gasket and that a pack of ten covers the number of joints being remade.
• If the joint is opened as part of a wider repair, check whether any other seals, washers or O-rings at the same assembly also need replacing.