You’ve just finished a routine backflush on your Richmond tankless water heater, and now there’s no hot water. No fan hum. No ignition click. No error codes. Just cold taps and mounting frustration. If you own a Richmond RMTG66DVP, this scenario is more common than you might think, especially when an IL (Ignition Lockout) code was already showing before maintenance.
The most likely culprit is a failed servo valve, the component that senses water flow and tells the unit to fire up. Even with confirmed power, gas, and water supply, the absence of fan activation means the control board never got the signal to start. This guide walks you through diagnosing and completing a Richmond tankless water heater repair, focusing on the fastest path to restoring hot water.
Decode the IL Code and Post-Flush Failure
What the IL Code Really Means
The IL code signals that your unit tried to ignite multiple times and failed. This safety feature prevents dangerous gas accumulation. If the IL code appeared before your backflush, it likely pointed to an underlying issue like restricted water flow or a weakening sensor that worsened during maintenance.
After a hard reset clears the code but hot water still doesn’t return, the problem goes deeper than ignition. The system can’t detect flow, so the startup sequence never begins.
Why Flushing May Have Triggered the Failure
Backflushing with vinegar is standard upkeep, but it can dislodge sediment. If the cold water inlet filter was removed during the process, debris may have traveled straight into the servo valve. This valve contains tiny internal passages that clog easily, halting flow detection.
Heated vinegar is unlikely to cause thermal damage since the servo valve handles high temperatures by design. However, mechanical blockage from sediment is a real and common risk.
Confirm the Absence of Ignition and Fan Activation
The Startup Sequence You Should Hear
When you open a hot water tap, your unit should follow this sequence:
1. Water flows through the system
2. The servo valve detects the flow
3. The control board activates the fan (inducer motor)
4. The gas valve opens and ignition occurs
5. The heat exchanger warms water on demand
If nothing happens, no fan, no click, no gas valve sound, then the sequence never started. This points directly to a flow detection failure.
Visual and Auditory Warning Signs
- No sound from the fan or gas valve
- No LED activity beyond normal standby
- Cold outlet pipe even after running water for 30 seconds or more
These signs confirm the unit isn’t entering ignition mode. Since power, gas, and water are all confirmed working, the missing link is the servo valve signal.
Diagnose Servo Valve Failure
How the Servo Valve Functions
The servo valve (Part # RTG20006JA) acts as a smart flow sensor. It uses a turbine and magnetic pickup to send a pulse signal to the control board. A weak or absent signal tells the board there’s no flow, so it won’t initiate the heating cycle.
This component sits on the cold water inlet side of the unit, making it the first part exposed to flushed vinegar and dislodged scale.
Why Cleaning Isn’t a Reliable Fix
Some technicians attempt to disassemble and clean the servo valve, but this approach has serious drawbacks:
– Internal turbine bearings are fragile
– The magnetic sensor can be damaged by probing
– No serviceable parts exist inside; only full replacements are available
Richmond and Rheem do not recommend field repair. The standard fix is straightforward: replace the servo valve.
Bench Testing Isn’t Practical for Homeowners
Testing the servo valve requires specialized equipment including a flow rig, a multimeter with frequency mode, and access to live water pressure. Even professionals rarely test this component off-unit. The manufacturer’s guidance is clear: replace, don’t troubleshoot.
Replace the Servo Valve (RTG20006JA)
Tools and Parts You’ll Need
- New servo valve (RTG20006JA)
- Adjustable wrench or 1-1/8″ flare wrench
- Pipe thread sealant rated for gas
- Bucket or towel for minor water spillage
- Screwdriver to remove the access panel
Warning: Turn off power, gas, and water supply before beginning any work.
Step-by-Step Replacement Process
-
Shut down the system completely
– Close the gas valve
– Disconnect power at the breaker
– Close both water isolation valves -
Relieve system pressure
– Open a hot water faucet to drain residual pressure -
Remove the access panel
– Unscrew and set it aside carefully -
Locate the servo valve
– Found on the cold water inlet line near the filter housing -
Disconnect the water lines
– Use a wrench to loosen the flare nuts on both sides
– Expect minor water leakage; place a towel underneath -
Remove the old servo valve
– Unscrew it from the manifold
– Inspect the port for visible debris -
Install the new servo valve
– Hand-tighten first, then wrench-tighten without overdoing it
– Reconnect both water lines -
Restore power and water
– Slowly reopen water valves to purge trapped air
– Reset power and gas -
Test the operation
– Turn on hot water at a faucet
– Listen for fan startup within 3 to 5 seconds
Address Filter Handling and Flush Best Practices
Never Remove the Filter During Backflush
The inlet filter plays a critical role during flushing. Removing it allows sediment to bypass filtration and scale chunks to enter sensitive components like the servo valve. The increased risk of clogging far outweighs any perceived benefit.
Best practice: Leave the filter in place during backflush. Vinegar circulates effectively without removing it.
Follow the Proper Flushing Procedure
According to the Richmond service manual:
1. Isolate the unit from home plumbing
2. Connect a flush kit to the service valves
3. Circulate 1 gallon of 50% vinegar solution for 45 to 60 minutes
4. Flush thoroughly with clean water
5. Reinstall filters; never remove them during the process
Pro Tip: Flush annually to prevent scale buildup, especially if you live in a hard water area.
Check Warranty Coverage and Contact Rheem
Is Your Unit Still Covered?
The RMTG66DVP typically includes:
– 10-year heat exchanger warranty
– 3-year parts warranty (may vary by installer or region)
At 3.5 years old, your unit may still qualify for parts coverage, especially if a certified technician handled the original installation.
How to Reach Rheem Support
- Phone: 1-800-432-8846 (Rheem Consumer Support)
- Website: www.rheem.com
- Have this information ready:
- Model number (RMTG66DVP)
- Serial number from the unit label
- Proof of purchase or installation records
- Installer information if available
Explain the situation clearly: “Servo valve failed after routine maintenance—seeking warranty evaluation.”
Rheem may offer:
– A free or discounted replacement part
– Expedited shipping options
– A referral to a local certified technician
Prevent Future Servo Valve Failures
Install a Whole-House Sediment Filter
Even with the unit’s internal filter, a 1-micron pre-filter on your main water line reduces scale and debris before it reaches the heater. Replace this filter every 6 to 12 months for optimal protection.
Schedule Annual Professional Maintenance
- Backflush with vinegar while keeping the filter in place
- Inspect inlet and outlet connections for scale
- Verify proper exhaust draft
- Check for any error codes or irregularities
Monitor Early Warning Signs
Don’t wait for complete failure. Watch for these early indicators:
– Delayed hot water response at faucets
– Fluctuating water temperatures during use
– Frequent IL or other error codes appearing
– Noticeably reduced flow rate
These symptoms signal early scale buildup or component wear that you can address before a full breakdown.
Frequently Asked Questions About Richmond Tankless Water Heater Repair
Why is my Richmond tankless water heater not producing hot water after a backflush?
The most common cause is a failed servo valve (RTG20006JA). Sediment dislodged during flushing can clog the valve’s tiny internal passages, preventing it from detecting water flow and signaling the control board to start the ignition sequence.
Can I clean the servo valve instead of replacing it?
Cleaning is technically possible but not recommended. The internal turbine bearings and magnetic sensor are delicate, and no serviceable parts exist inside. Richmond and Rheem advise full replacement rather than repair for reliable, long-term operation.
How do I know if my servo valve has failed?
Key indicators include no fan activation when you open a hot water tap, no ignition sequence, and no error codes after a hard reset. If power, gas, and water supply are all confirmed working but the unit stays cold, the servo valve is the prime suspect.
Is the RMTG66DVP still under warranty at 3.5 years old?
The unit typically includes a 10-year heat exchanger warranty and a 3-year parts warranty. At 3.5 years, you may still qualify for parts coverage. Contact Rheem at 1-800-432-8846 with your model and serial number to verify eligibility.
Should I remove the inlet filter before backflushing?
No. The inlet filter should remain in place during backflush. Removing it allows sediment to bypass filtration and enter sensitive components like the servo valve, significantly increasing the risk of clogs and component failure.
What happens if I keep cycling power without fixing the issue?
Repeated power cycling won’t resolve the underlying problem and may trigger new lockouts or error codes. Once the servo valve fails, replacement is the only reliable fix. Avoid unnecessary resets until the new part is installed.
Key Takeaways for Richmond Tankless Water Heater Repair
When your Richmond tankless water heater stops producing hot water after a backflush, a failed servo valve (RTG20006JA) is the most likely cause. The absence of fan activation or ignition, despite confirmed power, gas, and water, points to a broken flow signal. Cleaning might seem logical, but replacement is the only dependable solution.
Take action now:
– Order the new servo valve
– Follow safe replacement procedures
– Contact Rheem to check warranty eligibility
With the correct part and careful steps, you can restore hot water in under an hour. For your next maintenance session, remember to leave the filter in during flushing. This single habit could save you hundreds in future repairs and keep your Richmond RMTG66DVP running smoothly for years to come.
