29
Rheem Water Heater
Severity: MinorWhat Does This Error Mean?
Rheem condensing tankless Error 29 is a maintenance reminder, not a fault — it means the condensate neutralizer cartridge has reached the end of its rated life and needs replacing.
The unit will keep running for a while, but the condensate it dumps into your drain is now acidic enough to corrode metal pipes over time.
Replace the cartridge and clear the code from the service menu.
Affected Models
- Rheem RTGH-95XLN condensing tankless
- Rheem RTGH-95DVLN condensing tankless
- Rheem RTGH series (most condensing models)
- Some Performance Platinum condensing units
Common Causes
- Neutralizer cartridge has neutralized its rated volume of acidic condensate (typically 2-5 years depending on usage)
- Cartridge installed without resetting the counter on a previous service call
- Unit operating in heavy use environments (commercial-style residential setups)
How to Fix It
-
Confirm the cartridge needs replacement.
Locate the neutralizer — it's usually a white plastic tube about 6 inches long, mounted near the condensate drain line.
Pop the cap.
If the limestone or calcium carbonate media inside has visibly dissolved or turned yellow-brown, it's spent.
Even if it looks fine, the timer in the unit is the official measure. -
Order the right replacement cartridge.
Rheem sells a refill kit for their neutralizer.
Generic neutralizers from JJM, AO Smith, and others fit too — they're a standard size.
The media is just calcium carbonate chips; some homeowners refill the cartridge themselves.
Either is fine. -
Swap the cartridge.
Place a small bucket below the cartridge — there will be 100-200 ml of acidic water inside.
Unscrew the cap, lift out the old cartridge, drop in the new one.
Reseat the cap.
The drain line stays attached the whole time. -
Reset the maintenance counter.
On the front panel, hold the Mode button while pressing the Up arrow until you reach the Maintenance menu.
Find the neutralizer counter and press Reset.
The exact key sequence is in your unit's installation manual.
If you skip this step, Error 29 returns immediately even with a fresh cartridge. -
Add a calendar reminder.
Most cartridges last 2-3 years in heavy use, 4-5 in light use.
Set a calendar reminder for 24 months from today to check it again.
Replacing on schedule is much cheaper than replacing the heat exchanger after years of acidic condensate corroded the drain pan.
Frequently Asked Questions
Will the unit stop working if I ignore Error 29?
No — the unit keeps heating water normally.
What stops working is the protection of your drain pipes.
Condensate from a condensing tankless is acidic (pH 3-4) without neutralization.
Cast iron and copper drains corrode over months to years.
PVC drains tolerate it but local code in some jurisdictions requires neutralization.