Rheem tankless code 29: condensate drain problem, causes and fixes

Condensing tankless heaters produce acidic water, called condensate, as they pull heat from the exhaust. It drains through a neutralizer, which raises the pH, and then to a drain. When that path is blocked, Rheem shows code 29.

Code 29 applies to condensing models. It is one of the more fixable Rheem codes.

What to check

1. Find the condensate drain line and follow it from the unit to the drain.
2. Look for kinks, sagging sections holding water, debris or ice.
3. Check the neutralizer, the canister or cartridge on the drain line, for clogging. The media inside wears out and needs replacing periodically.
4. On a new installation, make sure no shipping cap was left on the drain fitting.
5. Reset the unit once the drain runs freely.

Winter and code 29

Drain lines in cold garages or near outside walls can freeze. If code 29 appears in cold weather, protect or reroute the line.

When to call a technician

Call a licensed technician if code 29 returns after the condensate drain and neutralizer are clear. The cause is then likely inside the unit, such as a blocked internal condensate trap or a faulty sensor, and those parts should only be tested and serviced by a professional.

Code 29 on other Rheem models

Rheem's current troubleshooting manual lists two meanings for code 29, and earlier models use a third wording:

For the "temperature too low" version, Rheem's checks cover the inlet and heat exchanger thermistors, the gas control valve and the water volume control valve. On condensing units, Rheem says to confirm the condensate drains properly before going further. On earlier models, the remedy is to clean the heat exchanger air inlet.

If you are not sure which version your unit shows, check whether it is a condensing model: those have a condensate drain line and neutralizer.