Code 29 with no hot water
The display shows code 29 and the burner will not stay on long enough to make hot water.
Start here: Check the condensate drain path and outside vent opening before assuming an internal failure.
Tankless water heater error help
Rinnai Tankless Water Heater Code 29
Direct answer: On a Rinnai tankless water heater, code 29 usually means the unit is having trouble with venting or condensate drainage, so it may shut down or stop heating to protect itself.
Most likely: The most common homeowner-level causes are a kinked or clogged condensate drain line, a full neutralizer or trap, or an outside vent termination blocked by debris, ice, or insect nests.
Start with the simple outside checks and the condensate drain path. If the vent looks damaged, you smell exhaust, or the code comes right back after a basic reset, stop there and bring in a qualified tankless tech. Reality check: this code often shows up after weather swings, nesting season, or a drain line that has slowly gunked up. Common wrong move: clearing the code over and over without fixing the blocked drain or vent.
Don’t start with: Do not start by replacing electronics or opening combustion parts. Most code 29 calls turn out to be airflow or condensate path problems, not a bad board.
Most likely first checkInspect the condensate drain tubing and outside vent termination for blockage or sagging water traps.
Stop and escalate ifYou smell flue gas, see melted vent parts, or find water inside the cabinet near electrical components.
Last reviewed: 2026-04-17
What code 29 usually looks like in the field
Code 29 only in cold or windy weather
The heater works some days, then faults during freezing weather, heavy wind, or after snow and ice buildup.
Start here: Look closely at the vent termination for ice, drifting debris, or a flap or screen packed with lint or nests.
Code 29 with water under the unit
You see dripping or a damp spot below the heater, sometimes along with the error code.
Start here: Follow the condensate tubing from the heater to the drain and look for a clog, kink, sag, or backed-up neutralizer.
Code 29 after a few minutes of shower use
Hot water starts normally, then the unit shuts down and posts the code once it has been running a bit.
Start here: That pattern often points to a partial vent restriction or a condensate drain that cannot keep up once the unit is producing more moisture.
Most likely causes
1. Clogged or kinked water heater condensate drain line
If condensate cannot leave the unit, water backs up where it should not and the heater may lock out with a venting-related fault.
Quick check: Look for a pinched tube, slime in clear tubing, a sag holding water, or a drain end shoved into standing water.
2. Blocked outside water heater vent termination
Leaves, insect nests, snow, ice, or wind-driven debris can choke the exhaust or intake path enough to trigger the code.
Quick check: Inspect the exterior vent opening with a flashlight and clear loose debris without disassembling sealed vent joints.
3. Condensate trap or neutralizer packed with debris
A trap or neutralizer can slowly fill with sediment and restrict flow even when the drain tube itself looks fine.
Quick check: If the drain line is clear but water is still backing up at the unit, the restriction may be at the trap or neutralizer body.
4. Venting installation problem or internal combustion issue
A sagging vent, separated joint, damaged fan path, or sensor-related combustion problem can also bring up code 29, especially if the code returns right away.
Quick check: If you smell exhaust, see staining around vent joints, or the code returns immediately after a reset, stop DIY and call for service.
Step-by-step fix
Step 1: Confirm the code and do one clean reset
You want to make sure you are chasing the right fault and not a one-off interruption from a power blip.
- Let the unit sit idle for a minute and confirm the display is actually showing code 29.
- Turn the heater off with its power button if accessible, wait about 30 seconds, then turn it back on.
- Run one hot water fixture and watch whether the code returns right away or only after a minute or two.
- Listen for anything unusual like a strained fan sound, gurgling water inside the unit, or rough ignition followed by shutdown.
Next move: If the heater runs normally and the code does not return, keep using it but move on to the vent and drain checks anyway. Intermittent code 29 usually comes back. If the code returns immediately or during the first hot water call, continue with the physical blockage checks.
What to conclude: A quick return points to a real venting or condensate problem, not just a temporary glitch.
Stop if:
- You smell exhaust or gas.
- The unit makes harsh banging, screeching, or repeated failed ignition sounds.
- Water is dripping onto wiring or the display area.
Step 2: Check the outside vent termination first
This is the fastest safe check, and outside blockage is common after storms, freezing weather, and nesting season.
- Go to the vent termination outside the house and inspect the opening with a flashlight.
- Remove loose leaves, spider webs, lint, or nesting material from the opening only.
- If there is frost or ice at the termination, clear only the visible buildup and see whether it reforms quickly.
- Make sure shrubs, stored items, or covers are not crowding the vent area.
- Do not take apart vent joints or force tools deep into the vent run.
Next move: If the heater runs normally after clearing the vent opening, you likely found the problem. Keep an eye on it over the next few hot water cycles. If the vent opening is clear or the code still returns, move to the condensate drain path.
What to conclude: A blocked termination can starve airflow or trap exhaust, and the unit will shut itself down rather than keep firing unsafely.
Step 3: Inspect the water heater condensate drain line
Code 29 often shows up when condensate cannot drain freely, especially on longer hot water runs.
- Locate the condensate drain tubing coming from the heater and follow it as far as you can to its drain point or neutralizer.
- Look for kinks, sharp bends, low spots full of water, or tubing that has slipped down and become pinched.
- If the tube end is accessible, make sure it is not submerged in standing water or packed with sludge.
- Straighten gentle kinks and support sagging sections so water can flow downhill consistently.
- If the outside of the tubing is dirty, wipe it clean so you can spot fresh dripping during the next test run.
Next move: If you correct a kink or sag and the heater now runs through a full hot water call without faulting, the drain restriction was likely the cause. If the tubing looks fine but the code remains, the restriction may be in the trap, neutralizer, or inside the unit.
Step 4: Look for a backed-up condensate trap or neutralizer
If the line is open but the unit still acts like condensate is not leaving, the blockage is often at the trap or neutralizer canister.
- Inspect any accessible condensate trap or neutralizer on the water heater drain path for obvious standing water, sludge, or leakage at fittings.
- Check whether the neutralizer body feels unusually heavy with water and debris compared with the tubing around it.
- If the setup has serviceable unions or caps and you know how they come apart, inspect only as far as you can do without forcing brittle plastic.
- Rinse only removable external drain components with plain water if they are clearly meant to be serviced and you can reinstall them correctly.
- Reassemble carefully, then run hot water again and watch for steady drainage and no returning code.
Next move: If the unit runs normally and you can see condensate draining steadily again, the trap or neutralizer was the likely choke point. If the code still returns, or the trap and neutralizer are not clearly serviceable, stop here and schedule tankless service.
Step 5: Decide between a simple drain repair and a service call
Once the easy blockage checks are done, the next move should be based on what you actually found, not guesswork.
- If you found a damaged, kinked, or leaking condensate drain tube, replace that tube with the correct size and routing for the heater setup.
- If you found a spent or clogged water heater condensate neutralizer and the rest of the system looks sound, replace the neutralizer and retest.
- If the code returns with a clear vent opening and a clear drain path, book service for venting inspection, fan path checks, and combustion-related diagnosis.
- Until the repair is complete, avoid repeated resets and do not rely on the heater if it is shutting down mid-use.
A good result: If the heater completes several long hot water calls without faulting and drains condensate normally, the repair path was successful.
If not: If code 29 still comes back after the visible drain and vent issues are corrected, the remaining causes are not good guess-and-buy territory for a homeowner.
What to conclude: A confirmed tube or neutralizer problem is a reasonable DIY fix. A recurring code after those checks usually needs professional venting or internal service.
Replacement Parts
Repair Riot may earn a commission from qualifying purchases, at no extra cost to you.
FAQ
Can I keep resetting code 29 and still use the water heater?
You can try one reset to confirm the fault, but repeated resets are not a fix. If the heater keeps posting code 29, it is telling you venting or condensate drainage is not right, and continued use is not a good bet.
Is code 29 usually a bad control board?
No. On this code, the common causes are much more often a blocked vent termination, a clogged condensate path, or a neutralizer or trap issue. Control and combustion parts are not the first thing to buy.
Why does code 29 show up only in winter?
Cold weather can expose vent and condensate problems fast. Ice at the vent termination, freezing in the drain path, or heavier condensate production during long runs can all bring the code up.
What if I cleared the vent opening and the code still comes back?
Then move to the condensate drain path. If the drain tube, trap, and any neutralizer are clear and the code still returns, the remaining causes usually need professional venting or internal diagnosis.
Is water under the tankless heater related to code 29?
Often, yes. If condensate cannot drain where it should, you may see dripping or pooling under the unit along with the error. Water inside the cabinet or on electrical parts is a stop-and-call condition.