C6 Error on Rheem RTGH-95DVLN Tankless Water Heater — Fix Guide

1. Home ›
2. Rheem ›
3. Tankless Water Heater ›
4. RTGH-95DVLN ›
5. C6

• Source: Official Rheem service manual
• Reviewed by: Geo Technical Editorial
• Published: March 1, 2026
• Updated: March 1, 2026

Safety notice: Start with user-safe checks only. Do not open sealed refrigerant systems, inspect gas-train components, or work on energized high-voltage parts unless you are qualified to service this appliance.

Error C6 on Rheem : Water flow sensor fault or insufficient flow rate. Follow the troubleshooting steps below to diagnose and fix this tankless-water-heater issue. ## What Error Code C6 Means on a Rheem RTGH-95DVLN Error C6 on the RTGH-95DVLN tankless heater indicates the water flow sensor has detected flow below the minimum activation threshold (typically 0.4–0.5 GPM), or the flow sensor itself has failed. The burner will not fire without adequate water flow. When C6 appears, the Rheem tankless water heater pauses normal operation to protect internal components from potential damage. Not every C6 fault requires a professional engineer — many are resolved through careful inspection and routine maintenance. Work through each diagnostic step below in sequence, starting with the simplest check, to identify the root cause efficiently before considering part replacement or arranging a service call. ## Symptoms - C6 on display; no hot water from tankless unit

• Cold water comes through when demand is low
• Hot water works fine at high flow but fails at low flow
• Flow sensor may be clogged with sediment ## Common Causes - Water flow sensor fault or insufficient flow rate ## Tools You May Need - Flathead screwdriver
• Flow meter (optional)
• Descaling kit ## Step-by-Step Repair Guide | Step | Action | Result | |------|--------|--------| | 1 | Ensure the cold water inlet valve at the unit is fully open. | Done — continue to step 2 if the issue persists. | | 2 | Check the inlet filter screen for sediment buildup — this is the most common cause of C6 in hard-water areas. | Done — continue to step 3 if the issue persists. | | 3 | Remove and clean the cold water inlet filter by rinsing under tap water. | Done — continue to step 4 if the issue persists. | | 4 | Test minimum flow by turning on a single hot water tap fully; if the unit fires with high flow, the flow rate from low-flow fixtures is insufficient. | Done — continue to step 5 if the issue persists. | | 5 | Consider installing a recirculation pump or removing aerators from low-flow faucets to increase minimum flow. | Done — if the fault remains, contact a qualified technician. | ## Safety Precautions Turn off the gas and cold water supply before removing the inlet filter or accessing the flow sensor. ## Estimated Repair Time and Difficulty Most tankless water heater error code C6 faults can be assessed and addressed in 30–90 minutes using the steps above. The diagnostic process requires only basic tools: a multimeter and standard screwdrivers cover the majority of checks described here. If a replacement part is required, allow 1–5 working days for delivery. A trained technician with access to the correct diagnostic equipment will typically resolve this type of fault within a single service visit. ## When to Call a Technician Contact a Rheem authorised service technician if: the fault persists after following all the steps above; if PCB-level or refrigerant-circuit work is required; or if you are not comfortable working with electrical or mechanical components. When calling, have the full model number, the error code displayed, and a brief description of any sounds or symptoms you noticed before the fault appeared — this helps the technician prepare the correct parts and tools. ## Frequently Asked Questions Q: What is the minimum flow rate for a Rheem tankless heater? Most Rheem tankless units require a minimum of 0.40–0.75 GPM (1.5–2.8 L/min) to activate. Check the product specifications for your exact model. Q: Will hard water affect the flow sensor? Yes — calcium deposits can partially block the turbine in the flow sensor, reducing its measured flow reading. Annual descaling of the heat exchanger and flow sensor is recommended. ### Is it safe to keep using my Rheem with error C6? If error C6 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the tankless-water-heater with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error C6 on a Rheem ? Repair costs for error C6 on the Rheem tankless-water-heater depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a Rheem-authorized service provider for an accurate estimate based on your specific situation. ### What does error code C6 mean on a Rheem tankless-water-heater? Error code C6 on Rheem tankless-water-heater models indicates Water flow sensor fault or insufficient flow rate. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue. ### Is it safe to keep using my Rheem with error C6? If error C6 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the tankless-water-heater with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error C6 on a Rheem ? Repair costs for error C6 on the Rheem tankless-water-heater depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a Rheem-authorized service provider for an accurate estimate based on your specific situation. ### What does error code C6 mean on a Rheem tankless-water-heater? Error code C6 on Rheem tankless-water-heater models indicates Water flow sensor fault or insufficient flow rate. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue.