In a quarter-turn lever tap the seal against flow is made by a replaceable ceramic-disc cartridge, so a tap that drips when closed indicates a worn or scaled sealing face inside that cartridge rather than a fault in the tap body, and the repair is component replacement rather than tap replacement. Because a two-lever mixer contains one independent cartridge per supply, the faulty side is identified by binary elimination — isolating each supply in turn at its service valve and observing which isolation stops the drip. The topic sits in domestic plumbing within building services, specifically sanitary tapware maintenance, and depends on the adjacent principles of upstream isolation, handed (mirror-image) valve operation, and dimensional interchangeability of aftermarket parts.
In a quarter-turn lever tap the seal against flow is made by a replaceable ceramic-disc cartridge, so a tap that drips when closed indicates a worn or scaled sealing face inside that cartridge rather…