Rheem 29: Condensate Drain / Low Heat Exchanger Temp
On a condensing Rheem tankless model, a 29 code most often means the condensate the unit produces during operation isn't draining the way it should; on any Rheem tankless model, the same code can also appear if the heat exchanger stayed too cool for too long.
Applies to: Rheem/Ruud tankless gas water heaters (condensate variant applies to condensing high-efficiency models)
What it means
On condensing models, the unit's condensate isn't draining. On any model, it can also mean heat exchanger temperature stayed too low for several minutes. The two triggers look identical on the display but point a technician in different directions, which is part of why it's worth describing the symptoms carefully to whoever diagnoses it — mention whether your unit is a condensing model and whether you've noticed any moisture near the base.
Most common causes
- Condensate shipping plug never removed at install
- Pinched, blocked, or improperly trapped condensate drain line
- Faulty thermistor or gas control valve
- Hot water demand exceeding the unit's rated flow capacity
What you can safely check yourself
- On condensing models, confirm the condensate protection plug was removed and the drain line isn't pinched, blocked, or fitted with an unnecessary P-trap
When to call a professional
The condensate line is clear but the code persists, or the low-temperature variant of this code appears — thermistor/valve diagnosis is needed.
Gas supply lines, gas control valves, and venting should only be worked on by a licensed plumber or HVAC technician. Mains/line-voltage electrical work should be done with the breaker off and, beyond a simple reset, by a qualified electrician or plumber.
What the fix costs
If the fix is just clearing a pinched or blocked condensate line, that's typically covered by a standard $75–$200 service call, per Angi's pricing guide. If it turns out to be a faulty thermistor or gas control valve instead, expect a parts-and-labor repair closer to $150–$450 installed, based on HomeGuide's contractor rate data. These are national ranges, not a quote for your unit — the technician needs to see which of the two triggers actually caused your code.
Related codes
- Rheem 1L — Scale Build-Up Warning
- Rheem 65 — Water Volume Control Valve Fault
- Rheem 14 — Overheat Limiter Tripped
- Symptom: water heater leaking from the base or bottom
All Rheem codes
Every Rheem water heater fault code — the full list on one page.
Sources
- Rheem/Ruud condensing tankless troubleshooting guide (manufacturer documentation)