🔍
Rinnai Water Heater ✅ Safe to Use

Rinnai Water Heater Error Code 79

Rinnai Water Heater error code 79: Water temperature sensor failure (bath fill).

Last reviewed: Last updated:

Methodology: We combine OEM HVAC documentation with field repair patterns, then review for safety-first troubleshooting.

Sources: HVAC manufacturer documentation, installation/service manuals, and technician-reported repair patterns.

Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.

Is it safe?
✅ Safe temporarily
Safe — unit stops when it can't fill. Check the supply hose and valve before calling a technician.
Can I fix it?
DIY Possible
Tools: Screwdriver set, Pliers, Multimeter
Repair cost
DIY: $15–$80 (inlet valve)
Pro: $100–$250
⏱ 20–40 min

What Does Error Code 79 Mean?

Rinnai Water Heater error code 79: Water temperature sensor failure (bath fill).

Part that typically fails: Water inlet valve / supply hose

Safe — unit stops when it can't fill. Check the supply hose and valve before calling a technician.

Symptoms You May Notice

How to Fix It Yourself

  1. 1 Check your owner's manual for model-specific guidance on error code reset procedures
  2. 2 Test the temperature sensor with a multimeter — replace if reading is outside spec
  3. 3 Inspect sensor wiring harness for damage or loose connections
  4. 4 If the error persists after reset and basic checks, contact a qualified technician
🛠️ Tools needed: Screwdriver set, Pliers, Multimeter · Time: 20–40 min
⚡ Quick tip: Always try a full power reset first — turn the unit off at the breaker, wait 30 seconds, restore power.

Frequently Asked Questions

What does Rinnai Water Heater error code 79 mean? ▼
Error code 79 on a Rinnai tankless water heater indicates: Water temperature sensor failure (bath fill). The unit has detected this condition and has limited or stopped operation to prevent further damage.
How do I fix Rinnai Water Heater error code 79? ▼
Start by powering the unit off for 30 seconds and restarting. If error 79 returns, the underlying cause (water temperature sensor failure (bath fill)) needs to be addressed. Check wiring connections and filters first before replacing components.
Is Rinnai error code 79 serious? ▼
It depends on the root cause. Some 79 errors resolve with a reset. Others indicate a failed component that requires professional repair. Don't continue operating with this error — it can lead to further damage.

More Rinnai Water Heater Error Codes

All Rinnai water heater codes → All Rinnai HVAC codes →

Was this page helpful?

Rate the helpfulness of this page