To replace a valve core in a sink's hot and cold tap, follow these steps: First, shut off the water supply by closing the main valve or individual shut-off valves beneath the sink. Next, disconnect the supply lines using pliers or a wrench, ensuring the water is fully drained. Remove the old valve core by unscrewing it from the base. Clean the seat and threads with a vinegar solution or a wire brush to remove debris. Insert the new valve core, aligning it properly, and screw it tightly into place. Reconnect the supply lines, turn on the water, and test for leaks or pressure issues. If leaks persist, recheck the installation or consider professional assistance.

Replacing a valve core is critical because worn or damaged cores cause water leaks, uneven temperature control, and reduced water pressure. According to the Environmental Protection Agency (EPA), household leaks can waste up to 10,000 gallons of water annually, equivalent to 90,000 gallons over 9 years. A faulty valve core also increases energy costs due to inefficient water heating from inconsistent flow. A 2021 study by the American Water Works Association found that 30% of water leaks in residential systems stem from valve failures, costing homeowners an average of $300 annually in water waste. DIY replacement saves 70–80% of repair costs compared to hiring a plumber, as reported by HomeAdvisor. Regular maintenance prevents property damage, such as mold growth from leaks, which affects 85% of U.S. homes annually, according to the National Association of Home Builders. Ensuring a functional valve core maintains water efficiency, safety, and cost-effectiveness, aligning with sustainability goals and long-term home preservation.