Rinnai error code 10 means an air supply or exhaust blockage: the tankless water heater cannot draw in enough combustion air or push its exhaust out. On the condensing RU and RUR models, a full condensate trap sets the same code. Start outside at the vent terminal and clear anything blocking it, then check the condensate line and, on indoor RU and RUR units, the internal air filter.
What Rinnai error code 10 means by series
Rinnai's manuals give code 10 two slightly different names. The RU series manual and the RUR series manual call it "Air Supply or Exhaust Blockage/Condensate Trap is Full". The VC manual for the RL models and the Value Series manual for the V models call it "Air Supply or Exhaust Blockage".
The checks differ too. This table sorts the code 10 remedies from those four manuals into the ones you can look at and the ones Rinnai leaves to a professional.
| Check | Series it applies to | Who does it |
|---|---|---|
| Nothing blocking the vent inlet or exhaust | All four (RU and RUR: indoor models) | You |
| Vent pieces properly connected | RL, V | You can look; a pro fixes |
| Condensate line not blocked | RU, RUR | You |
| Internal air filter clean | RU, RUR indoor models | You, following the manual |
| Approved vent materials and vent length within limits | All four | Licensed technician |
| High-altitude or DIP switch settings | All four | Licensed technician |
| Fan free of debris and turning freely | All four | Licensed technician |
| Check valve not stuck between fan and burner | RU, RUR | Licensed technician |
Code 10 remedies from Rinnai's RU (100000467), RUR (100000508), VC (100000244) and Value Series (100000258) manuals, opened October 2026. The VC and Value manuals mark every check after the first two "licensed professional only". For other codes, see our full Rinnai error code list.
If you smell gas, stop. Rinnai's manuals say not to light any appliance, not to touch electrical switches or use a phone in the building, and to call your gas supplier from a neighbor's phone. Leave the house first and make the call from outside.
Step 1: Check the vent terminal outside
Find where the heater's vent pipes leave the house, on the wall or the roof. The VC and Value manuals tell owners to check that nothing is blocking the flue inlet or exhaust. Look for debris, insects, or anything stacked against it or growing over it.
In winter, look for snow and ice. The RU manual says to keep the area around the flue terminal free of snow and ice, because the heater will not work properly if the combustion air or exhaust pipes are blocked or partly blocked. Its maintenance section adds the screens in the vent termination to the list of things to inspect.
Clear only what you can reach safely from outside. The RU manual's rule is simple: if the vent is blocked and cannot be easily cleared, contact a trained and qualified professional. Do not take vent pipes apart. Rinnai's diagnostic guide warns never to run the heater with the vent piping disconnected.
On RL and V models, also look along any length of vent pipe you can see. The manuals list "check all vent components for proper connections" as an owner check. If a joint has pulled apart, leave the repair to a technician.
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Step 2: Check the condensate line on RU and RUR models
The RU and RUR models are condensing water heaters, and they drain condensate through a line to a drain. Rinnai's diagnostic code guide explains why this sets code 10. If the condensate line clogs or freezes, water backs up into the trap inside the heater, and the heater shuts off to prevent spillage.
The RU manual says to make sure condensate is flowing and that the end of the drain is open to the air. Keep the line free of snow and ice, and check that it is not blocked or clogged. If the line feeds an accessory condensate pump, a pump fault shows as code 25 instead.
Step 3: Clean the air filter on indoor RU and RUR models
Indoor RU and RUR models have an internal air filter, and a dirty one is on Rinnai's code 10 list. The RU manual, section 6.2, gives the cleaning steps. Its maintenance section also says repairs and maintenance should be done by a trained and qualified professional, so if you are not comfortable removing the front panel, have a pro do this.
Before any maintenance, the manual says to turn off the electrical power at the plug or the circuit breaker, because the temperature controller does not cut the power. It also says to close the manual gas valve below the heater and the incoming water supply. Then, per section 6.2:
- Press On/Off to switch the heater off. The display goes blank.
- Remove the four screws holding the front panel and take it off.
- Find the filter in the upper right-hand corner and pull it out by the "FILTER Pull to Clean" tab.
- Scrub the filter area with mild dish soap and a soft bristle brush, then rinse it with clean water.
- Dry it with a lint-free towel.
- Check it for debris that could restrict airflow. If it still looks dirty, clean it again.
- Put the filter back, refit the panel, then turn the power, gas and water back on.
The manual is firm on two points. Do not run the heater without the air filter in place. If the filter looks damaged, contact a trained and qualified professional for a replacement filter assembly.
The VC and Value manuals do not list an internal air filter for the RL and V models, so this step does not apply to them.
Step 4: Try the hot water again
Open a hot tap and watch the controller. Rinnai's owner tables give no separate reset step for code 10, so the real test is whether the heater now runs. Our guide to resetting a tankless water heater covers power cycling if the display needs a fresh start.
If code 10 comes back, stop there. A related code, 17 (venturi blockage) on RU and RUR models, tells you to run the code 10 checks first and call Rinnai if they do not fix it.
When to call a technician
Call once the vent terminal is clear, the condensate line flows and the filter is clean, and code 10 still returns. The rest of Rinnai's list means opening the unit or changing its settings. The manuals warn that some checks should be done only by a trained or licensed professional, and that consumers should never attempt anything they are not qualified to do. Also call if you find a damaged or disconnected vent pipe, a blockage you cannot reach, or a frozen condensate line you cannot thaw safely.
What a technician checks for code 10
Rinnai's diagnostic guide, written for professionals only, lists the steps. In broad order, the technician:
- confirms the condensate line drains and cleans the internal air filter
- inspects the whole intake and exhaust system for clearances, materials and seated joints
- runs a short test with the exhaust section removed, to see whether the blockage is in the vent
- checks the equivalent vent length, counting each elbow, against the manual's limits
- looks for a vent pipe crushed by foam sealant where it passes through the wall
- removes the fan to inspect the fan wheel, housing and air duct, and the check valve
- confirms the high-altitude setting
- inspects the burner chamber and heat exchanger fins for debris
If none of that finds it, the guide names a faulty fan motor, a damaged fan wiring harness or a faulty circuit board as other causes. If your heater shows code 12 instead, see our Rinnai code 12 guide.
Frequently asked questions
How do I reset Rinnai error code 10?
Rinnai's owner tables give no separate reset for code 10. Clear the cause first: the vent terminal, the condensate line on RU and RUR models, and the internal air filter on indoor RU and RUR units. Then open a hot tap. If the heater runs, the blockage is gone. If code 10 returns, the cause is inside the vent system or the unit, and a licensed technician needs to find it.
Can snow cause Rinnai code 10?
Yes. Rinnai's RU manual says to keep the area around the flue terminal free of snow and ice, because the heater will not work properly if the combustion air or exhaust pipes are blocked or partly blocked. It says the same about the condensate drain line. If the vent is blocked and you cannot easily clear it, Rinnai says to contact a trained and qualified professional.
Where is the air filter on a Rinnai tankless water heater?
On indoor RU and RUR models, the RU manual puts it behind the front panel in the upper right-hand corner, with a tab marked FILTER Pull to Clean. Turn off power, gas and water first, then remove the four panel screws. The VC and Value manuals do not list an internal air filter for RL and V models. Never run the heater without the filter in place.
Is it safe to keep using a Rinnai with code 10?
Do not try to force the heater to run past code 10. Rinnai's manuals say it will not work properly with a blocked vent, its diagnostic guide says a backed-up condensate trap shuts it off to prevent spillage, and the same guide warns never to run it with vent piping disconnected. If you smell gas, leave the house and call your gas supplier from outside.
What is the difference between Rinnai code 10 and code 17?
Code 10 is an air supply or exhaust blockage on all four series in our table. Code 17 appears on RU and RUR models and means a venturi blockage. Rinnai's manual says to work through the code 10 checks first for code 17, and if those do not fix it, to have the venturi checked and call Rinnai's technical department.
Founder of Home Caprice. Benas started the site to simplify HVAC after dealing with the heating and cooling in his first apartment.
