As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: WATER TANK WENT FROM FULL TO COMPLETELY EMPTY WITHIN 25 MIN OF TAKEOFF. AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO PHX WHERE IT LANDED SAFELY WITHOUR FURTHER INCIDENT.REPLACED FORWARD DRAIN VALVE AND ACCOMPLISHED A SATISFACORY LEAK / OPERATIONAL CHECK PER AMM 38-14-41.