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T020

T020 - Lower Tank Sensor open

Rheem · Water Heaters

What does T020 mean?

The lower tank (inlet) temperature sensor (thermistor) is detected as open. Check the wiring to the sensor.

Common Causes

  • Lower tank temperature sensor wiring issue
  • Faulty lower tank temperature sensor

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the wiring to the lower tank temperature sensor.

  2. 2

    Refer to the use and care manual for further troubleshooting.

  3. 3

    Contact technical support if the condition persists.

Browse all codes in this manual (70)
Verified technical data. Last updated: April 2026

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1111 - Gas shut-off valve is not fully open1212 - Gas service interrupted or LP gas low13Hot and cold water lines reversed
Source: Rheem Water Heaters
Open Manual (Page 43)Search more codes in this manual