Rheem Water Heater Code 29: What It Means and How to Fix It

By Dan Mercer · Published October 5, 2026 · Updated October 6, 2026 · Codes covered: 29 · Sources

Verify in your manual: The meaning (Neutralizer is clogged) is from the Service Error Code Chart in Rheem's RTGH condensing tankless Use and Care manual. Rheem's non-condensing RTG chart doesn't list code 29, and a Ruud error code list gives 29 a different meaning on some models. Check the chart in your own Use and Care manual.

Code 29 on a Rheem condensing tankless gas water heater means the neutralizer is clogged. That's the part of the condensate drain system that treats the acidic water a condensing heater makes. Rheem's chart sends this code to a dealer or qualified service technician, but a few safe, no-tool checks on the drain line can tell you what to report, and sometimes reveal an obvious blockage.

This 3-minute fix saved 0 homeowners a technician visit this month.

What the 29 code means

The Service Error Code Chart in Rheem's RTGH (Super High Efficiency Condensing) tankless Use and Care manual lists code 29 as "Neutralizer is clogged." The solution it gives is "Contact a dealer or qualified service technician."

Here's the background. A condensing tankless heater pulls extra heat out of its exhaust, and that makes water (condensate). Rheem's manual warns that "The condensate coming from the water heater is known to be acidic." It recommends an external neutralizer so the condensate doesn't corrode metal drains. The neutralizer holds a treatment medium that the condensate flows through on its way to a drain. When that path is clogged, the condensate can't get away, and the heater stops with 29.

Rheem's manual also says that a blocked condensate drain makes an error code show on the remote, and that the drain must be cleared when that happens.

This code is for condensing models. Rheem's non-condensing RTG chart doesn't include 29. A Ruud tankless error code list gives 29 a different meaning ("Heat Exchanger Outlet Temp. Too Low") on some models, so check the chart in your own manual.

Look-alike codes that mean something different:

• Code 11: the gas shut-off valve isn't fully open.
• Code 12: gas service was interrupted, or LP gas is low on propane models.
• Code 14: the water heater is overheating.

Likely causes (most common first)

1. Neutralizer medium clogged or used up. Rheem tells owners to check yearly that the medium is still present, and to replace the neutralizer if it's depleted.
2. Blocked or kinked condensate drain line between the heater, the neutralizer and the drain.
3. Drain outlet under water or sealed off. Rheem says the end must be open to the air.
4. Frozen condensate line in cold weather.
5. A drain line that doesn't slope down, or one that's narrower than the heater's drain connection. Rheem says the pipe must be at least the same diameter along its whole length. That's an installation issue for a pro to correct.
6. A problem inside the heater's condensate system. Only a technician can check it.

How to fix it, step by step

Test a hot tap after each step.

1. Do Rheem's reset. Close all hot taps, turn the heater off at the remote, wait about 5 minutes, turn it back on, and open a hot tap.
2. If 29 stays, power-cycle. Turn off the tap and the heater, unplug it, wait about 30 seconds, plug it back in, and try again.
3. Check the drain outlet. Make sure the end of the condensate line is open to the air and not under water.
4. Straighten an obvious kink in a flexible drain tube, if you can do it by hand without disconnecting anything.
5. Let a frozen line thaw in a warm space, and tell your technician about it. Don't apply a torch or open flame anywhere near the heater.
6. Don't take the neutralizer apart while the code is active. Condensate is acidic, and Rheem's chart sends code 29 to a technician.
7. Call for service if 29 keeps coming back. Turn off the tap and heater, write down the code, and call. That's the step Rheem's manual gives.

Test the part

There's no meter test for a homeowner here. The neutralizer and drain can only be inspected by eye, and anything inside the heater sits behind a cover with live 120-volt wiring. Here's what you can safely check:

1. Unplug the water heater and turn off the gas. Pull the plug (or switch off the breaker on hard-wired models), then turn the gas shut-off valve on the outside of the unit clockwise to OFF.
2. Follow the condensate line from the heater to the drain. Look for kinks, crushed spots, sags that hold water, or ice.
3. Look at the neutralizer, if it has a clear housing. You're checking whether medium is still inside and whether it looks packed or crusted. Don't open it.
4. Look at the drain outlet. It should be open to the air and not under water.
5. Look for drips or corrosion around the heater, the neutralizer and nearby metal. Rheem warns that untreated condensate can corrode metal.
6. Wear gloves if you have to touch a wet line. The condensate is acidic.

When you're done, follow the Operating Instructions label on the heater to turn the gas back on and restore power.

Safety notes

When to call a pro

Code 29 is a "call a technician" code on Rheem's chart. Call a dealer, licensed plumber or qualified service technician if:

• Code 29 comes back after a reset and the drain line looks clear.
• The neutralizer medium looks used up, packed or crusted. Rheem's maintenance list says a depleted neutralizer should be replaced. Unless your neutralizer kit's own instructions say it's owner-serviceable, let the technician do it and check the drain at the same time.
• The drain line freezes, doesn't slope downward, or empties under water. Rerouting or insulating it is installer work.
• You see corrosion or condensate leaking from the heater itself.
• The heater is under warranty. Have the model number, serial number and installation date ready.

Rheem's manual says to start with your installer, plumbing contractor or licensed service agent. Rheem's contact page lists water heating support at (800) 432-8373, Monday to Friday, 7 a.m. to 7 p.m. Central.

FAQ

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