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How to fix Rheem tankless water heater code 12?

Alton Alexander
By Alton AlexanderUpdated on June 4th, 2022

Rheem tankless water heater code 12 indicates that the water heater is not providing enough hot water. This can be caused by a variety of factors, including a low water pressure, a clogged water heater filter, or a faulty thermostat.

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1. Check the gas supply to the unit

  1. Turn off the electricity to the water heater.
  2. Inspect the gas supply lines for any obstructions.
  3. If there are any obstructions, remove them.
  4. If the gas supply lines appear to be in good condition, turn on the electricity to the water heater and check for gas leaks.
  5. If there are no gas leaks, replace the gas line if it is old or corroded.
  6. If there are gas leaks, replace the gas line or the water heater.

2. Check for any blockages in the gas supply line

  1. Turn off the gas supply to the water heater.
  2. Check for any obstruction in the gas supply line.
  3. If there is an obstruction, remove the obstruction.
  4. Reconnect the gas supply line.
  5. Turn on the gas supply to the water heater.
  6. Check for any gas leaks.

3. Check the pressure regulator

  1. Open the water heater and locate the pressure regulator.
  2. Remove the pressure regulator.
  3. Inspect the system for any leaks.
  4. Replace the pressure regulator if necessary.

4. Check the igniter

  1. Open the water heater and locate the igniter.
  2. Remove the igniter if needed.
  3. Inspect the igniter for signs of damage.
  4. If the igniter is damaged, replace it.

5. Check for any blockages in the exhaust vent

1.Turn off the power to the water heater. 2.Remove the screws that hold the cover on the water heater. 3.Locate and remove the exhaust vent. 4.Check for any blockages in the exhaust vent. 5.Replace the exhaust vent if necessary.

6. Check the thermocouple

  1. Remove the cover off the water heater.
  2. Locate the thermocouple in the water heater.
  3. Check the connections on the thermocouple.
  4. Replace the thermocouple if needed.