As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RDU - FLT 32 - AIRCRAFT DEPARTED RDU FOR LAX. EN ROUTE, CREW HAD YELLOW SYSTEM LOW PRESSURE WARNING ON ECAM AND RETURNED TO RDU. UPON SHORT FINAL HAD YELLOW RESERVOIR LOW LEVEL. MAINTENANCE FOUND LOOSE B-NUT FITTING ON YELLOW SYSTEM ACCUMULATOR BOTTLE. TIGHTENED B-NUT. OPS CHECK AND LEAK CHECK GOOD IAW A320 MM 29-13. (X)