Rheem tankless water heater error code 35 typically indicates a gas valve or flame sensing issue that requires immediate safety verification.
Table of Contents
- What does error code 35 mean on a Rheem tankless water heater?
- Why is my Rheem tankless water heater showing error code 35?
- What are the quick fixes to try first for error code 35?
- What should I check next if the initial reset fails?
- Which fix matches your specific Rheem tankless water heater symptom?
- When should you stop troubleshooting and call a professional?
- What information should you have ready before calling for service?
- How can you prevent error code 35 from coming back?
What does error code 35 mean on a Rheem tankless water heater?
Error code 35 on a Rheem tankless water heater typically points to a gas supply anomaly or a flame failure during operation.
This code activates when the control board detects an interruption in proper gas delivery or ignition. Because meaning can vary slightly depending on your specific indoor or outdoor model line, always confirm the exact description in your owner manual.
- Indicates a disruption in the normal gas combustion process inside the unit.
- Triggers automatically to prevent unburned gas accumulation and ensure household safety.
- May appear during high hot water demand or intermittent utility supply pressure drops.
- Requires checking external gas valves and internal electronic components carefully.
- Varies slightly across different Rheem tankless generations, so check your manual.
Why is my Rheem tankless water heater showing error code 35?
Common causes include a partially closed gas supply valve, low gas pressure, or a dirty flame rod sensor.
When your appliance attempts to ignite, multiple safety checks must pass. If the gas pressure drops below operational thresholds or soot buildup insulates the flame sensor, the unit locks out and displays error code 35 to alert you.
- Main gas supply valve is restricted or only partially open.
- Gas meter regulator experiencing temporary pressure drops during peak usage.
- Flame sensor rod covered in carbon buildup preventing proper flame detection.
- Loose or corroded wiring harness connecting the gas valve to the control board.
- Blocked exhaust or intake venting restricting proper combustion airflow.
What are the quick fixes to try first for error code 35?
Perform a simple system reset and verify that your main gas supply valve is fully open before proceeding.
Before contacting a professional, you can safely attempt basic external resets. Always turn off the electrical power breaker before inspecting any external connections to protect yourself from high-voltage components.
- Turn off the power switch on the water heater and trip the dedicated circuit breaker.
- Locate the main gas supply valve near the unit and ensure it is turned fully parallel to the pipe.
- Wait sixty seconds to allow the internal control board capacitors to fully discharge.
- Turn the dedicated circuit breaker back on and power up the water heater.
- Open a hot water tap fully to test if the unit ignites normally without error.
What should I check next if the initial reset fails?
Inspect the venting pathways for blockages and check external gas regulator settings for proper delivery pressure.
If basic power cycles do not clear error code 35, external environmental factors or minor component fouling may be the root cause. Carefully inspect the immediate surroundings of your water heater installation.
- Inspect the outdoor intake and exhaust vent terminals for nests, leaves, or physical obstructions.
- Confirm that other gas appliances in your home operate properly to rule out a utility gas outage.
- Unplug the appliance power cord before checking external wiring harnesses for loose plug connections.
- Gently wipe down any accessible exterior sensor wiring to ensure secure metal contact.
- Test hot water operation again after confirming all external pathways are clear and secure.
Which fix matches your specific Rheem tankless water heater symptom?
Match your exact operational symptom to the corresponding likely cause and recommended corrective action below.
Different manifestations of error code 35 point toward distinct underlying mechanical or utility issues. Use this quick reference table to identify your exact situation and determine the appropriate response.
| Symptom | Likely cause / fix |
|---|---|
| Error appears instantly on startup | Closed gas valve; open fully. |
| Error appears during heavy use | Low gas pressure; call utility. |
| Ignition clicks but fails | Dirty flame sensor; clean gently. |
| Intermittent code in high winds | Venting blockage; clear terminals. |
When should you stop troubleshooting and call a professional?
Stop immediately and call a licensed technician or your gas utility if you smell gas or suspect gas valve failure.
Gas appliances demand strict safety adherence. Because gas leaks, faulty gas valves, and sealed combustion chamber repairs pose severe safety hazards, amateur intervention beyond basic resets is dangerous and prohibited.
- You detect any odor of natural gas or propane near the appliance.
- The troubleshooting steps fail to clear error code 35 after multiple attempts.
- Internal gas valve replacement or manifold adjustment is required.
- Electrical control board components show visible burn marks or component failure.
- You feel uncomfortable or uncertain about performing any external diagnostic step.
What information should you have ready before calling for service?
Gather your exact water heater model number, serial number, warranty status, and a list of attempted troubleshooting steps.
Having accurate details ready when contacting Rheem support or a local plumbing professional accelerates diagnosis. Locate the silver specification rating plate on the outer casing of your water heater to find the necessary identifiers.
- Exact model number found on the rating plate sticker.
- Full unit serial number indicating manufacturing date and version.
- Proof of purchase or installation date for warranty verification.
- Clear record of the error code number and troubleshooting steps you tried.
- Description of gas supply type and recent utility work in your home.
How can you prevent error code 35 from coming back?
Schedule annual professional maintenance and keep outdoor intake vents clear of seasonal debris and dust.
Proactive upkeep protects sensitive electronic flame sensors and ensures stable gas combustion pressures. Regular preventive care minimizes unexpected hot water interruptions throughout the lifespan of your appliance.
- Schedule annual professional flushing and combustion inspection by a certified technician.
- Inspect outdoor intake and exhaust terminals monthly for spider webs or leaves.
- Keep the area surrounding the tankless water heater clean and free of dust buildup.
- Test pressure relief valves and electrical connections periodically for secure operation.
- Register your appliance with Rheem to receive critical safety and maintenance updates.
Frequently Asked Questions
Can I clear Rheem error code 35 by pressing the reset button?
Yes, pressing the reset button on the remote control or power cycling the unit can clear temporary glitches. However, if the underlying gas supply or flame sensing issue persists, the code will quickly return until the root cause is resolved.
Is it safe to operate my home when error code 35 is active?
When error code 35 triggers, the water heater automatically shuts off gas flow to the burner for safety. While the unit itself is in a safe lockout state, you should address the underlying cause promptly and avoid tampering with internal gas components.
Does error code 35 mean my gas valve is completely broken?
Not necessarily. While a faulty gas valve can trigger this code, it is much more frequently caused by a temporary drop in household gas pressure, a closed supply valve, or a dirty flame sensor rod that simply requires gentle cleaning.
How much does it cost to repair a Rheem tankless water heater error 35?
Repair costs vary widely depending on your geographic area and the specific part needing replacement. Simple fixes like cleaning a sensor cost very little, whereas replacing a gas control valve or circuit board typically ranges from one hundred to four hundred dollars in parts and labor.
Where is the model number located on a Rheem tankless water heater?
The model and serial numbers are printed on a silver or white specification rating label affixed to the outer metal cabinet of the water heater. You can easily find this label by looking at the side or front panel of your unit.
Bottom Line
Start by performing a safe power reset and verifying that your main gas supply valve is fully open. If error code 35 persists, contact a licensed professional immediately.
Sources
- Rheem Owner Manual
- Rheem Support Page
- Manufacturer Technical Bulletin