Ariston 65154087 O-Ring D=11.5 D=2.65

The Ariston O-Ring D=11.5 D=2.65 is a small elastomer sealing ring used across Ariston heating and hot water appliances. It sits in a machined groove or against a joint face and compresses when the two mating parts are brought together, forming a watertight barrier at that connection. It is supplied under Ariston part number 65154087.

O-rings of this type are a service item rather than a permanent component. Heat, pressure cycling and limescale gradually harden the rubber, so the ring loses the resilience it needs to seal and starts to weep.

• Weeping or dripping at the joint the ring seals, often worse once the appliance is up to temperature
• The ring feels hard, flattened or brittle when removed, rather than soft and springy
• Cracking, nicks or a flattened cross-section visible on the ring itself
• Scale, corrosion or mineral deposits built up around the sealing face
• Water staining or chalky trails on components below the joint
• Pressure loss traced to a joint rather than to the boiler or cylinder itself

• Confirm 65154087 against your appliance's parts list or serial number, as the same appliance family can use different seals at different joints
• Measure the old ring against D=11.5 and D=2.65 before fitting, since a ring of the wrong cross-section will not seal
• Note the alternative number 1593164 when cross-referencing other suppliers' listings
• Inspect the groove and mating faces for scoring or corrosion; a damaged sealing face will not hold with a new ring alone