29
Noritz Tankless Water Heater
Severity: ModerateWhat it means
Noritz code 29 appears on condensing models and means condensate isn't draining the way it should — the drain line, trap, or neutralizer cartridge is blocked, so water is backing up inside the unit.
A condensing tankless makes acidic water as a normal by-product, and it has to flow out freely.
When it can't, the unit faults to protect itself.
It's almost always a plumbing-side fix, not an electronics one.
Affected Models
- Noritz NRC66, NRC83, NRC98, NRC111 (condensing)
- Noritz NRCP series (with built-in pump)
- Noritz EZ98, EZ111
- Noritz GQ-C series condensing units
- Other Noritz condensing models fitted with a neutralizer
Common Causes
- Condensate drain hose kinked, pinched, or routed uphill
- Drain trap clogged with sediment or biofilm
- Neutralizer cartridge spent and packed solid (no longer letting water through)
- Floor drain or condensate pump it empties into backed up
- Hose disconnected and condensate pooling in the base instead
- Condensate frozen in a line that runs through an unheated space
How to Fix It
-
Trace the condensate hose from the unit.
Follow the small hose leaving the bottom of the unit.
It should run downhill the whole way to a floor drain, a standpipe, or a condensate pump — no uphill loops, no kinks, no sharp bends.
Straighten or re-route anything that isn't draining freely. -
Flush the trap.
Disconnect the hose at the unit and at the trap, and flush the trap with warm water until it runs clear.
Sediment and slime build up here over time.
While it's off, check the hose itself isn't clogged. -
Check the neutralizer cartridge.
If your install has a neutralizer (a small canister of media that de-acidifies the condensate), a spent one packs into a solid plug and stops flow.
Replace the media or the whole cartridge per the manual — they're an annual-ish wear item on a condensing unit. -
Make sure where it drains isn't backed up.
If the condensate empties into a floor drain that's clogged, or a small condensate pump that's failed, water has nowhere to go.
Clear the floor drain or service/replace the pump. -
Reset and watch for it to return.
With the drain flowing freely, power-cycle the unit and run hot water for several minutes.
Code 29 should stay gone.
If it comes back with a clear drain, there may be a blockage inside the unit's internal condensate path — that's a Noritz service call.
Frequently Asked Questions
Do I really need to replace the neutralizer cartridge?
If your Noritz install has one, yes — it's there to keep the acidic condensate from eating your drain pipes, and a clogged one will keep throwing code 29.
Most need fresh media every year or two depending on usage and local water.
If you're not sure whether your install includes a neutralizer, look for a small canister plumbed into the condensate line below the unit.