DIY Error Codes

Rinnai Tankless water heater Code 10

Something is restricting air in or exhaust out, or (SENSEI condensing models) the condensate trap is backed up.

Check the condensate drain line and the outside vent terminals. Anything inside the heater or vent pipe is pro work.

Start the fix →When to call a pro ↓
Full answer & models

Rinnai code 10 means: Air Supply, Exhaust Blockage or Condensate Trap is Full. Check the condensate drain line and the outside vent terminals. Anything inside the heater or vent pipe is pro work.

Applies to: SENSEI™ SeriesNon-SENSEI™ Series
Also searched as: Rinnai code 10, Rinnai error 10, Rinnai error code 10

If you smell gas, leave the building and call your gas supplier from a neighbor's phone. Do not touch switches or use any phone inside.
Why
If you smell gas: do not try to light any appliance, do not touch any electrical switch, and do not use any phone in your building. Leave and call your gas supplier from a neighbor's phone; if you cannot reach them, call the fire department. Rinnai states that only trained and qualified professionals may follow its diagnostic-code service instructions, and that power, gas and water must be turned off before servicing. Never operate the heater with any vent pipe disconnected. Do not adjust the internal gas valve. Burn hazard (Rinnai): hot exhaust and vent may cause serious burns; keep small children and animals away, and hot water outlet pipes can be hot to touch.

What 10 means

Something is restricting air in or exhaust out, or (SENSEI condensing models) the condensate trap is backed up.

More detail
Rinnai's diagnostic-code guide (page 10) titles code 10 "Air Supply, Exhaust Blockage or Condensate Trap is Full". Rinnai's guide is written for trained, qualified professionals, so this page lists only the owner-level checks and tells you when to stop.

5-minute checks

Fix it step by step

Step 1 of 3

  1. Check the condensate drain line

    • 10 min
    • None
    • DIY

    Safety: If you smell gas, leave the building and call your gas supplier from a neighbor's phone. Do not touch switches or use any phone inside.

    A clogged or frozen line backs up into the trap and shuts the heater off.

    More detail

    Check the condensate drain line.

    Rinnai's guide, code 10 step 1: if the condensate drain line becomes clogged or freezes, it backs up into the condensate trap, which shuts the heater off and sets code 10.

    Did the code clear?

  2. Look for restrictions at the vent terminals

    • 5 min
    • None
    • DIY

    Safety: If you smell gas, leave the building and call your gas supplier from a neighbor's phone. Do not touch switches or use any phone inside.

    Outside only. Do not disconnect vent pipe.

    More detail

    Look for restrictions at the vent terminals.

    Rinnai's guide lists debris in the vent system and improper vent clearances as causes. An owner can look at the outside terminations; Rinnai warns never to operate the heater with the vent disconnected.

    Did the code clear?

  3. Call a licensed pro

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a licensed pro.

    Rinnai's remaining code 10 steps (vent disassembly, fan removal, burner and heat exchanger cleaning, altitude settings) are for qualified professionals.

    Still showing 10?Need a pro → call a pro

Code cleared. Nice work.

Watch the display for a day to make sure it stays clear.

Back to top

Fixed after any step? Watch the display for a day to make sure it stays clear. Still 10 after step 3? call a pro.

Call a pro if…

  • The drain line and vent terminals are clear and code 10 returns.
  • Any vent pipe looks damaged, sagging or disconnected.

FAQ

What does Rinnai code 10 mean?

Air supply, exhaust blockage, or a full condensate trap (condensing SENSEI models), per Rinnai's diagnostic guide.

Source: Rinnai, Troubleshooting Tankless Water Heater Diagnostic Codes (100000652), page 10. Written by the DIY Error Codes team. Updated 2026-10-16. DIY Error Codes is independent and not affiliated with or endorsed by Rinnai.