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Rinnai code 10 (air supply or exhaust blockage): what to check

By How House Works EditorialBased on Rinnai manualsChecked against sources Updated

Rinnai display

10

“Air Supply or Exhaust Blockage/ Condensate Trap is Full”

RU/RUR/RSC, RX, RE/REP, V, RL/VC · SENSEI RU Installation and Operation Manual, p. 73; SENSEI RUR Installation and Operation Manual, p. 72; SENSEI RSC Installation and Operation Manual, p. 72; SENSEI RX/CX Tech Sheet, p. 1; RE Series Installation and Operation Manual, p. 49; REP Series Installation and Operation Manual, p. 48; Value Series Installation and Operation Manual, p. 34; V53De Installation and Operation Manual, p. 28; VC Series Installation and Operation Manual, p. 37; Troubleshooting Tankless Water Heater Diagnostic Codes, p. 12–15
Owner checks, then technician

RE/REP, Value, V53De and VC tables: "Air Supply or Exhaust Blockage" (RE manual, p. 49). The condensate trap applies to SENSEI and SENSEI RX/CX models only (troubleshooting guide, p. 12).

What it means

Code 10 is Rinnai’s code for a blocked combustion air supply or exhaust. Rinnai says the heater will not function properly if the combustion air or exhaust vent pipes are blocked or partly blocked RU manual, p. 77.

On the condensing RU, RUR, RSC and RX models, the same code also covers a full condensate trap; the troubleshooting guide limits that part to SENSEI and SENSEI RX/CX models p. 12. If the condensate drain line clogs or freezes, condensate backs up into the trap inside the heater, and the heater shuts off to prevent spillage and shows code 10 p. 12.

Check these first

Rinnai’s tables warn that consumers should never attempt any action they are not qualified to perform RU manual, p. 73; Value manual, p. 34. The V53De manual adds: call a licensed professional for any remedy that involves gas or electricity, or if you have any doubt about doing it yourself V53De manual, p. 28. If you smell gas, the Value and V53De manuals put one step before those in the box above: leave the premises Value manual, p. 28; V53De manual, p. 22.

  1. Outside, check that nothing blocks the vent termination, on the air intake side or the exhaust side Value manual, p. 34; RU manual, p. 73. Clear snow and ice from around the flue terminal RU manual, p. 77.
  2. On Value and VC models, also look over the vent components you can see for proper connections; the table lists this as an owner check Value manual, p. 34; VC manual, p. 37. Repairs are not: venting materials and vent length are “licensed professional only” items Value manual, p. 34.
  3. On RU, RUR, RSC and RX models, check the condensate drain line RU manual, p. 73; SENSEI RX/CX Tech Sheet, p. 1. Condensate should be flowing, the line should not be blocked or frozen, and its end should be open to the air, not under water RU manual, pp. 54, 76–77.
  4. If the vent is blocked and you cannot easily clear it, contact a trained and qualified professional RU manual, p. 76.

The tables give no separate reset step for code 10.

When to call a licensed technician

  • The internal air filter on indoor RU, RUR, RSC and RX units RU manual, p. 73. It sits behind the front panel pp. 78–79, and Rinnai says the panel comes off only for service, maintenance or replacing internal parts p. 8.
  • Approved venting materials and vent length RU manual, p. 73; Value manual, p. 34. On RE and REP models, the vent length must match the vent length set in the parameters RE manual, p. 49.
  • The high altitude setting RU manual, p. 73. Only trained and qualified professionals may change parameter settings p. 8.
  • The fan: debris, whether the wheel turns freely, and the check valve between the fan casing and the burner body RU manual, p. 73.
  • DIP switches on Value and VC models Value manual, p. 34; VC manual, p. 37.
  • Other causes the troubleshooting guide names: a defective fan motor, its wiring harness or the PC board, and on Non-SENSEI models the manifold gas pressure settings pp. 13, 15.

Notes for different models

The RE, REP, Value, V53De and VC tables name code 10 without the condensate trap RE manual, p. 49; Value manual, p. 34. The V53De is an outdoor model V53De manual, p. 22; its owner check is that nothing blocks the inlet or exhaust p. 28.

On SENSEI and RX models, the remedy for code 17 (venturi blockage) starts with the code 10 remedies RU manual, p. 74.

Related Rinnai codes

  • 17 “Venturi Blockage”
  • 25 “Condensate Pump (Accessory)”
  • 61 “Combustion Fan”

All Rinnai codes

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Sources

  1. Rinnai America Corporation. Troubleshooting Tankless Water Heater Diagnostic Codes. 100000652(03), 5/2024; for trained and qualified professionals. Accessed Oct 12, 2026.
  2. Rinnai America Corporation. SENSEI RU Installation and Operation Manual. 100000467(07), 1/2021; cover title: Tankless Water Heater (Residential) Installation and Operation Manual; listed on rinnai.us as N Series Residential Condensing Installation and Operation Manual. Accessed Oct 12, 2026.
  3. Rinnai America Corporation. SENSEI RUR Installation and Operation Manual. 100000508(07), 1/2021; cover title: Tankless Water Heater (With Pump) Installation and Operation Manual. Accessed Oct 12, 2026.
  4. Rinnai America Corporation. SENSEI RSC Installation and Operation Manual. 100000773(01), 1/2023. Accessed Oct 12, 2026.
  5. Rinnai America Corporation. SENSEI RX/CX Tech Sheet. 100000849, U362-0875(00); no printed date or page numbers (p. 1 is the PDF page). Accessed Oct 12, 2026.
  6. Rinnai America Corporation. RE Series Installation and Operation Manual. 100000722(03), 6/2022; cover title: Tankless Water Heater Installation and Operation Manual. Accessed Oct 12, 2026.
  7. Rinnai America Corporation. REP Series Installation and Operation Manual. 100000726(03), 3/2022; cover title: Tankless Water Heater (With Pump) Installation and Operation Manual. Accessed Oct 12, 2026.
  8. Rinnai America Corporation. Value Series Installation and Operation Manual. 100000258(10), 4/2021; cover title: Direct Vent Tankless Water Heater Installation and Operation Manual. Accessed Oct 12, 2026.
  9. Rinnai America Corporation. V53De Installation and Operation Manual. 100000561(05) (from the file name; no printed revision or date). Accessed Oct 12, 2026.
  10. Rinnai America Corporation. VC Series Installation and Operation Manual. 100000244(12), 8/2019; cover title: Direct Vent Tankless Water Heater Installation and Operation Manual. Accessed Oct 12, 2026.