Baxi O-Ring 100mm 5115768

The Baxi O-Ring 100mm (part number 5115768) is a circular elastomer seal used inside Baxi heating appliances. It sits in a machined groove or seating face and compresses when the joint is assembled, closing the gap between mating components so that water or system fluid cannot escape. O-rings of this type are a service item: they are replaced whenever a joint is broken down or whenever the original seal has hardened, flattened or perished.

• A weep or drip at a joint that was previously dry, often showing as a crust of scale or a damp patch on the casing or floor beneath.
• The seal feels hard, brittle or flattened when handled, rather than springy and round in section.
• Visible cracking, splitting, nibbling or a flattened profile on the ring where it has taken a permanent set.
• Water tracking along a pipe or fitting after the appliance has been reassembled following other work.
• Discolouration or swelling of the rubber where it has been in contact with system water or inhibitor.

• Confirm the part number against your appliance's data badge or installation manual, as sealing components vary between models and revisions.
• Note the alternative number 1118198 — it may appear on older documentation or parts listings for the same item.
• Measure the old ring before disposal if you are unsure of the size, and check the seating groove for scale or corrosion that could damage a new seal on fitting.
• If the joint also uses a gasket or fibre washer, check whether that item is serviceable separately before reassembly.