To replace the valve core in a cold and hot water faucet, first shut off the water supply using the main valve or individual shut-off valves. Disassemble the faucet by unscrewing the handle, stem, and escutcheon plate. Remove the old valve core by twisting and pulling it out. Clean the seat with a seat wrench or replace it if damaged. Insert the new valve core, ensuring it seats properly. Reassemble the faucet in reverse order, tightening components gradually. Test the faucet for leaks and adjust the stem if water flow is uneven.

Replacing the valve core addresses leaks caused by mineral buildup, which affects 30% of U.S. households, according to the Environmental Protection Agency (EPA). Over time, debris like calcium and magnesium ions accumulates in the valve seat, creating gaps that reduce water efficiency. A faulty valve core can waste up to 10 gallons of water daily, contributing to higher utility bills and environmental strain. The EPA estimates that fixing leaks could save the average household 10% on water costs annually. Additionally, improper installation risks cross-contamination in plumbing systems, as improper seating may allow dirty water to enter the supply. Data from the American Water Works Association (AWWA) shows that 15% of water loss in municipal systems stems from leaks, often linked to aging valve cores. Regular replacement ensures optimal performance, durability, and compliance with plumbing codes, which mandate leak-proof valve installations. Neglecting this task may lead to costly repairs or water main breaks, as seen in a 2022 study by the University of California, Davis, which linked aging valve cores to 22% of emergency plumbing repairs in urban areas.