Rheem · ProTerra 120V plug-in
Rheem ProTerra 120V plug-in error code T300
Water vor Not Installed [sic; as printed]
What it means
Water Leak Sensor Not Installed
Also listed in: Residential 120V Plugin With HydroBoost Heat Pump Water Heater (Shared Circuit) Use & Care Manual, AP22654 Rev 01, page 31
What Rheem says to do
These steps involve electrical testing or parts replacement. Rheem's manuals tell owners to leave that work to a qualified service technician.
1. Check to ensure water leak sensor is installed. 2. Check wiring connections to sensor from board. 3. Check resistance to sensor to determine whether sensor or board should be replaced (See ohm reading chart for correct readings).
Last checked 2026-10-03.
Safety first
- CAUTION: For your safety DO NOT attempt repair of electrical wiring, thermostats, or other safety devices. Refer repairs to qualified service personnel. (p.28)
- WARNING: If the water heater has been subjected to fire, flood or physical damage, disconnect all power to water heater, and DO NOT operate the water heater again until it has been checked by a qualified service technician. (p.19)
From the manufacturer's manual for this series.
The same code on other models
Codes mean different things on different heaters. Match the series to the model number on your rating label.
- Rheem ProTerra / Performance Platinum hybrid (Gen V, 240V): T300
- Rheem HB Duct Ready Series (touchscreen): T300
Other ProTerra 120V plug-in codes
- A004 (Comp.Shutdown: Discharge-Suction Trip)
- A005 (Compressor Shutdown: Discharge Temp High)
- T005 (Compressor Shutdown: Discharge Temp High)
- A006 (Suction Temperature Too Low)
- T006 (Suction Temperature Too Low)
- T009 (Compressor wiring may be faulty)
- A009 (Compressor wiring may be faulty)
- A101 (Suction Temperature Sensor Failure)
- A102 (Ambient Temperature Sensor Failure)
- A103 (Lower Heater Temp Sensor Failure)
- A104 (Upper Heater Temp Sensor Failure)
- A105 (Evaporator Temp Sensor Failure)
- A106 (Discharge Temp Sensor Failure)
- A107 (Water Detected on Floor: Check For Leaks)
- A108 (Condensate Blocked: Unclog Line)
- A130 (Unit Off/Air Temp Freezing: Enable Unit)
- T131 (Clean Filter Reminder)
- T132 (Water Heater difficulty satisfying demand)
- A120 (Shutoff Valve Can't Close Error)
- A121 (Shutoff Valve Can't Open Error)
- A122 (Shutoff Valve Inputs in Error)
- A123 (Shut-Off Valve Not Installed)
- A200 (High Water Temp! [ECO] Call Tech Service)
- A502 (Time Clock needs to be programmed)
- A503 (Time Clock not advancing time properly)
- T504 (WiFi Chip Communication Error)
- A900 (Controller Fault: Call Tech Service)
- T901 (Controller Fault: Call Tech Service)
- A902 (Controller Fault: Call Tech Service)
- A903 (Controller Fault: Call Tech Service)
- A904 (Controller Fault: Call Tech Service)
- A905 (Controller Fault: Call Tech Service)
- A906 (Power Board Temp. Protection Sensor Failure)