How to Replace a Boiler Flue Seal (UK)
Renew flue O-rings and gaskets on Worcester, Vaillant, Baxi and Ideal boilers. Cures CO alarm nuisance trips.
Worcester BoschVaillantBaxiIdeal
When to replace
Every flue disturbance. Every annual service on horizontal flues in enclosed loft spaces. Any FGA reading above 100 ppm CO in the room ratio.
OEM part numbers
- Worcester 60/100 flue — 87172080130 (double O-ring set).
- Vaillant 60/100 — 981147.
- Baxi 60/100 — 5121380.
Fit
Silicone grease sparingly. Insert flue with a straight push — twisting rolls the O-ring.
Frequently asked questions
- Do EPDM flue seals need silicone?
- Yes — dry O-rings roll and tear on insertion.
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