After replacing a faucet's valve core, persistent leaks often stem from improper installation, damaged components, or residual issues. Common causes include misaligned valve seats, faulty O-rings, incorrect tool usage, or undetected pipe leaks.

Data from the American Water Works Association (AWWA) reveals that 30% of faucet leaks post-repair result from installation errors, such as improper seating or overtightening. A 2021 study by the EPA found mineral deposits in pipes reduce seal effectiveness by up to 40%, exacerbating leaks. Additionally, 25% of valve cores fail within six months if O-rings are mismatched or degraded, per plumbing industry surveys. For instance, a 2020 report by the National Association of Home Builders (NAHB) noted that 18% of homeowners reported recurring leaks after valve core replacements, often due to incompatible parts or incomplete cleaning of the valve seat. These issues highlight the importance of precision during replacement and post-inspection testing. Residual water pressure or cross-connection problems may also contribute, as 15% of leaks in multi-story buildings originate from upstream pipe failures, according to the Center for Water Quality. Addressing these factors through meticulous installation, quality parts, and pressure testing ensures long-term functionality.