Captain reported the APU fuel shutoff valve remained open; causing a fuel loss requiring an air turn...

Attributes
ACN	1748894
Time
Date	202006
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Make Model Name	A321
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	APU Fuel System
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Fuel Issue

Narrative:

Climbing through 23;000 ft. To 37;000 ft. I was PF (pilot flying). As I scrolled through the systems display pages I noticed the APU lp fuel valve indication on the fuel sd was amber indicating the valve is open with the APU master southwest in the off position. I then noticed the left fuel tank quantity was decreasing at a rate of about 20 lbs. Every 10 seconds as the fuel was now showing a 400 lb. Imbalance. The first officer addressed the communication; we [requested priority handling]; and began an air return to ZZZ. During the descent; I noticed APU lp changed to a white indication indicating the valve had closed. The landing was under mlw (maximum landing weight); arff (airport rescue and fire fighting) inspected the aircraft for leaks and found none. We taxied to the gate with no further incident.

Original NASA ASRS Text

Title: Captain reported the APU fuel shutoff valve remained open; causing a fuel loss requiring an air turnback and precautionary landing.

Narrative: Climbing through 23;000 ft. to 37;000 ft. I was PF (Pilot Flying). As I scrolled through the systems display pages I noticed the APU LP fuel valve indication on the FUEL SD was amber indicating the valve is open with the APU MASTER SW in the off position. I then noticed the left fuel tank quantity was decreasing at a rate of about 20 lbs. every 10 seconds as the fuel was now showing a 400 lb. imbalance. The FO addressed the COM; we [requested priority handling]; and began an air return to ZZZ. During the descent; I noticed APU LP changed to a white indication indicating the valve had closed. The landing was under MLW (Maximum Landing Weight); ARFF (Airport Rescue and Fire Fighting) inspected the aircraft for leaks and found none. We taxied to the gate with no further incident.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.