Code 29 with no hot water at all
The display shows code 29 and the heater will not stay running long enough to make hot water.
Start here: Start with the outside vent termination and air intake area. A hard blockage is the most common first find.
Tankless water heater error help
Ruud Tankless Water Heater Code 29
Direct answer: On a Ruud tankless water heater, code 29 usually means the unit is seeing a venting or condensate problem and will stop heating to protect itself. The first things to check are a blocked vent termination, a sagging or clogged condensate drain line, or water sitting where it should not be inside the vent path.
Most likely: Most of the time, this turns out to be an airflow restriction at the vent outside or a condensate drain issue, not a part you should buy first.
Start with what you can see and reach safely: look for debris, ice, nests, standing water, or a kinked condensate line. Reality check: this code often shows up after weather swings, wind, or deferred maintenance. Common wrong move: clearing the code over and over without fixing the vent or drain problem just sends the heater right back into lockout.
Don’t start with: Do not start by replacing boards, sensors, or gas parts. On this code, the simple outside and drain checks are the money checks.
If the vent outside is blockedClear the obstruction, then reset power and test hot water again.
If the condensate line is full, kinked, or slimed upStraighten and clear the line before assuming an internal failure.
Last reviewed: 2026-04-17
What code 29 usually looks like in the house
Code 29 after rain or freezing weather
The error shows up after a storm, cold snap, or wind event, sometimes with water around the unit or ice at the vent.
Start here: Look for ice, wind-driven debris, or water trapped in the vent or condensate line.
Code 29 that clears, then comes back
Power cycling gets you one short hot water run, then the code returns.
Start here: Check the condensate drain path for a partial clog or sag that lets water back up again.
Code 29 with odd exhaust smell or moisture
You may notice dampness near the venting, unusual exhaust odor outside, or dripping where it normally stays dry.
Start here: Stop using the heater until you inspect the vent path and condensate routing. That points to a venting problem, not a simple reset issue.
Most likely causes
1. Blocked vent termination or intake opening
Leaves, lint, insect nests, snow, or a plastic bag at the outside termination can choke airflow and trigger this code fast.
Quick check: Go outside and inspect the vent ends closely with a flashlight. Do not just glance from a distance.
2. Clogged, kinked, or sagging condensate drain line
If condensate cannot leave the heater, water can back up and interfere with proper venting or pressure sensing.
Quick check: Follow the condensate tube from the heater. Look for dips full of water, slime, a pinch point, or a disconnected section.
3. Water intrusion or vent pipe issue
A loose joint, bad slope, or water getting into the vent can change how the unit senses exhaust flow.
Quick check: Look for staining, drips, or wet spots around the vent connection area near the heater.
4. Internal venting sensor or control fault
If the vent and condensate path are clear and the code returns immediately, the unit may have a failed sensing component or control issue.
Quick check: Only consider this after the visible vent and drain checks are clean and the error still comes right back.
Step-by-step fix
Step 1: Check the vent termination and intake outside first
This is the safest and most common fix. A blocked vent end can trip code 29 even when the heater itself is fine.
- Turn off the hot water demand so the heater is not trying to fire while you inspect.
- Go to the outside vent termination and air intake openings.
- Remove leaves, lint, spider webs, nests, snow, or any loose debris by hand.
- If there is light ice at the opening, let it melt naturally or clear it gently without prying on the vent parts.
- Make sure nothing stored outside is crowding the vent area.
Next move: Restore power if needed, run a hot water fixture, and see whether the heater stays on without throwing code 29. Move to the condensate drain check. A partial drain blockage is the next most likely cause.
What to conclude: If clearing the vent fixes it, the heater was protecting itself from poor airflow or exhaust restriction.
Stop if:
- You smell gas anywhere near the heater or vent area.
- The vent pipe is loose, separated, cracked, or badly corroded.
- You see scorching, melting, or soot around the vent termination.
Step 2: Inspect the condensate drain line for backup or sagging
On condensing tankless units, a backed-up condensate line is a very common reason this code returns after a reset.
- Turn off power to the water heater before touching the drain tubing near the unit.
- Find the condensate line coming off the heater and follow it as far as you can.
- Straighten any sharp kinks and correct any deep sag that can hold water like a trap where it should not.
- If the line is removable and accessible, disconnect it carefully and flush it with warm water into a bucket or drain.
- Reconnect the line securely and make sure it runs with a steady downward path.
Next move: Power the heater back on and test a steady hot water draw for several minutes. Go on to a close visual check around the heater and vent connection area for water or vent damage.
What to conclude: If the code clears after the drain line is corrected, condensate was backing up and interfering with normal venting.
Step 3: Look for water marks, loose venting, or obvious installation drift near the heater
Once the easy outside and drain checks are done, the next useful clues are physical signs that exhaust or condensate is not moving the way it should.
- With power off, inspect around the top and sides of the heater for dampness, staining, or white mineral tracks.
- Check visible vent connections for looseness, sagging, or joints that look shifted.
- Look for condensate dripping where it should not, especially near the vent connection area.
- If the intake screen or accessible air opening is dusty, clean only the reachable surface gently without opening sealed combustion sections.
Next move: If you find and correct a simple loose support or obvious external drain issue, retest the heater. At this point, repeated code 29 with no visible blockage usually needs service-level diagnosis.
Step 4: Reset once after the vent and drain checks are complete
A single clean reset is reasonable after you have corrected the likely cause. Repeated resets without a fix just mask the problem.
- Make sure the vent area is clear and the condensate line is reconnected and draining properly.
- Turn power to the heater off for about one minute, then restore power.
- Open one hot water fixture and let it run long enough for the heater to light and stay operating.
- Watch for the code to return and note whether it fails immediately or only after a minute or two.
Next move: If hot water stays steady and the code does not return, keep an eye on it over the next day or two, especially after heavy use or weather changes. If code 29 returns right away or during the same draw, stop here and schedule service for venting-sensor or internal condensate-path diagnosis.
Step 5: Set up the service call with the right notes
Good notes save time and keep you from paying for a guess. On this code, the tech needs to know what you already ruled out.
- Write down exactly when code 29 appears: immediately, after a minute, only in cold weather, or only during long hot water draws.
- Tell the service company whether you found any vent blockage, water in the condensate line, or moisture around the venting.
- Mention any recent storm, freeze, roof work, siding work, or pest activity near the vent termination.
- Leave the heater off if you noticed exhaust odor, loose venting, or water near electrical components.
A good result: A good service call should move straight to venting verification and internal condensate or sensor checks instead of random part swapping.
If not: If the company wants to start with a board or gas part before confirming venting and condensate conditions, get a second opinion.
What to conclude: You have done the safe homeowner checks. The remaining causes are usually internal, fitment-specific, or combustion-related and are not good guess-and-buy repairs.
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FAQ
What does code 29 mean on a Ruud tankless water heater?
In plain terms, it usually means the heater is not happy with venting or condensate flow and shuts down to protect itself. The common homeowner-side causes are a blocked vent end, a backed-up condensate line, or water where it should not be in the vent path.
Can I just reset the heater and keep using it?
Only once after you have checked and corrected the obvious vent or condensate issue. If the code comes back, repeated resets are not a fix and can hide a venting problem that needs service.
Is code 29 a bad control board?
Usually not as a first guess. Boards and internal sensors are farther down the list than vent blockage, drain backup, or water intrusion. Rule out the simple physical causes first.
Why did code 29 show up after rain or freezing weather?
Weather can block the vent with ice, blow debris into the termination, or change how condensate drains. That is why an outside vent check and condensate line check are the first two moves.
Should I clean the condensate line myself?
If the line is easy to reach and disconnect safely, a simple warm-water flush is reasonable. Stop if water is trapped inside the cabinet, the line setup is confusing, or you would need to open sealed sections to continue.
When should I call a pro for code 29?
Call if the vent looks damaged, you smell gas or exhaust, the code returns right away after the basic checks, or there is moisture inside the cabinet or around wiring. At that point the remaining work is usually internal venting, sensing, or combustion diagnosis.