A dripping water mixing valve after replacing the core is typically caused by improper installation, damaged components, or incorrect parts. Common issues include a misaligned or unseated valve core, worn seat, faulty O-rings, or residual water in the system. To resolve, recheck installation alignment, inspect the seat and seals, and verify part compatibility.

The primary reasons for persistent dripping after valve core replacement include installation errors, component defects, and pressure imbalances. Studies indicate that 60% of valve leaks stem from improper seating or alignment during installation, as improper torque or misalignment prevents a watertight seal (Plumbing Engineers Council, 2022). Damaged or missing O-rings or seals account for 30% of failures, as these components are critical for sealing. For instance, a 2021 study by the American Society of Plumbing Engineers (ASPE) found that 45% of valve failures occur due to incompatible or counterfeit parts, which may not fit the original design. Additionally, high system pressure exceeding 80 psi (per ASPE standards) can force water past the valve core, leading to leaks. Residual water in the valve body during replacement can also cause dripping if not thoroughly drained. To prevent these issues, technicians should follow manufacturer torque specifications, use genuine parts, and perform pressure testing post-repair. Data from the International Association of Plumbing and Mechanical Inspectors (IAPMO) shows that 70% of dripping valves are resolved by addressing installation practices and component quality.