What was found
F/A REPORTS NO POTABLE WATER FOR COFFEE MAKER OR SINKS. GROUNDED - YES. AIR TURNBACK - DIVERSION TIME 30 MINUTES - TROUBLESHOOT IN REF TO B737-800 FIM 38-10 TASK 803 FOUND FILL/OVERFLOW VALVE NOT CLOSING COMPLETELY AND LEAKING WHEN SERVICE DOOR CLOSED. REMOVED AND REPLACED FILL/OVERFLOW VALVE, AS SUGGESTED BY FIM 38-10 TASK 803. REF B737-800 AMM 38-11-03. WATER FLOWS IN COFFEE MAKERS AND SINKS. A/C OK FOR SERVICE.