A plumber is called to a residential property where the kitchen faucet has a constant drip from the spout even when fully closed. The faucet is a single-handle cartridge type. What is the most likely cause of this issue?

Question: A plumber is called to a residential property where the kitchen faucet has a constant drip from the spout even when fully closed. The faucet is a single-handle cartridge type. What is the most likely cause of this issue?

Answer options:

• Low water pressure in the domestic water system.
• A worn or damaged O-ring seal around the faucet spout.
• A faulty aerator at the end of the spout. ✅ A worn or defective ceramic disc or rubber washer within the cartridge.

Correct answer: A worn or defective ceramic disc or rubber washer within the cartridge.

Explanation: A constant drip from a single-handle cartridge-type faucet spout is most commonly caused by a worn or defective ceramic disc or rubber washer within the cartridge. The cartridge is responsible for controlling water flow and temperature, and its internal seals are critical for preventing leaks. Other options like low water pressure or a faulty aerator would present different symptoms, and a worn O-ring would more likely cause a leak around the spout base rather than a constant drip from the spout itself.