On the covered Rheem tankless gas water heater, 29 means error. On high-efficiency (condensing) units only, Rheem's pocket manual says condensation is not draining. It also lists a second explanation for 29: the heat exchanger temperature was too low for more than 3 minutes. First, look for a kinked or blocked condensate drain line.
Differential
Likely causes of “Rheem tankless gas water heater code 29”, and how to tell them apart
- 1
A kinked or blocked condensate drain line
What separates it Condensation is not draining
How to confirm Clear the line
- 2
A frozen or blocked condensate trap
What separates it Winter faults
How to confirm Thaw and clear it
- 3
A heat exchanger temperature that stays too low
What separates it The temperature is low for three minutes
How to confirm Technician diagnosis
- 4
A sensor fault
What separates it The reading is wrong
How to confirm Technician checks the thermistor
- 5
A failing neutralizer
What separates it The condensate path is blocked
How to confirm Technician service
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether it is a condensing (high-efficiency) unit
- Whether the drain is kinked
- The ambient temperature
Try in this order
0 of 5 completedWhat to do first
ReversibleLook for a kinked or blocked condensate drain line.
Correct only the documented fault domain
ReversibleRheem's pocket manual splits code 29 into two diagnostic sequences, one for condensation not draining (high-efficiency units only) and one for heat exchanger temperature too low for more than 3 minutes. Rheem's steps when a code shows: turn on a hot water faucet and recheck the remote control display. If the code stays, turn off the faucet and the water heater, unplug the water heater for about 30 seconds and plug it back in, follow the chart for your code, restart the water heater and recheck. If the code is still shown, turn off the faucet and the water heater, note the code and call for service. If a code is not in the chart, turn the water heater off immediately and call for service.
Look for a kinked drain line
ReversibleOn a condensing unit.
Check the condensate trap
ReversibleFor blockage.
Note the unit type
ReversibleHigh or mid efficiency.
Model-specific
What is true of this model and not of its siblings
- Condensing units make water
- A high-efficiency tankless heater extracts so much heat from its exhaust that the vapour condenses, and the condensate must drain away through a line. A kink or blockage stops it and triggers the code.
- Two causes
- Rheem's pocket manual lists a second explanation: the heat exchanger temperature was too low for more than three minutes. The sequences are different and need a technician.
- Cold weather
- A condensate line in an unheated space can freeze, so check it after a hard frost.
- Which meaning applies
- Rheem's pocket manual gives two explanations. On high-efficiency units, condensation is not draining. On any unit, the heat exchanger temperature was too low for more than three minutes. Knowing your unit type narrows it down.
- The condensate path
- A condensing unit makes liquid water that drains through a trap and a hose, often to a neutralizer. A kinked hose, a clogged trap or a frozen line stops the drain and trips the code.
- Low temperature
- If the heat exchanger stays cold, the burner may not be producing heat, or a sensor may misread. That diagnosis needs a technician with a meter.
- Condensation and short draws
- A tankless heater that is used in very short bursts, such as a few seconds of hot water at a time, never warms the heat exchanger to its working temperature. Combustion gases then condense on the cold metal and the control may report low heat exchanger temperature. Running hot water for longer, or fitting a recirculation arrangement that the maker approves, can reduce the effect. A technician also checks the condensate drain and the vent for blockage.
Stop boundary
When this stops being a self-service repair
- !Rheem's manual splits this code into two diagnostics for a technician
- !Condensate drains apply to high-efficiency units only
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does 29 mean on a Rheem tankless gas water heater?+
Error. On high-efficiency (condensing) units only, Rheem's pocket manual says condensation is not draining. It also lists a second explanation for 29: the heat exchanger temperature was too low for more than 3 minutes.
Does it apply to every unit?+
The condensate cause applies to high-efficiency units only.
What can I check?+
The condensate drain line.