To fix an uneven thermostatic shower head, start by descaling mineral deposits using a white vinegar solution (1 part vinegar to 1 part water) or a commercial shower head cleaner. Soak the head for 30 minutes, then scrub with a soft brush. Next, check the diverter valve for blockages or misalignment, which can disrupt water flow. If issues persist, replace the thermostatic cartridge. Ensure the shower handle is adjusted properly to maintain temperature balance.

Mineral buildup from hard water is the primary cause of uneven temperature and pressure in thermostatic shower heads. Hard water contains calcium and magnesium ions that react with soap, forming scale that clogs nozzles and reduces water distribution. A 2021 study by the Environmental Protection Agency (EPA) found that 85% of U.S. households experience hard water, with calcium hardness levels exceeding 100 ppm in 40% of cases. Scale buildup reduces shower head efficiency by up to 30%, as confirmed by a Journal of Building Engineering report (2022). Diverter valve issues, often caused by debris or wear, account for 25% of thermostatic shower malfunctions, per a 2023 survey by the International Association of Plumber-Heating-Electrical Contractors (IAPHEC). Replacing a faulty thermostatic cartridge resolves internal temperature regulation failures, which occur in 15% of cases after prolonged use. Regular descaling every 3–6 months and annual diverter inspections are recommended to prevent recurrence.