Rheem Electric Tankless Water Heater Troubleshooting Guide

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Is your Rheem electric tankless water heater giving you trouble—cold water, blinking lights, or strange error codes? Don’t stress! Most issues are simple to fix at home, and many problems are just a matter of cleaning, resetting, or swapping out an inexpensive part. This complete troubleshooting guide will walk you through the most common Rheem electric tankless water heater issues, step-by-step solutions, and when to consider a replacement or essential accessory for lasting hot water comfort.

Quick Picks: Best Tools & Replacement Parts for Rheem Electric Tankless Water Heaters

Common Rheem Electric Tankless Water Heater Problems

  • No Hot Water
  • Flashing/Error Codes
  • Low Water Flow or Temperature
  • Unit Won’t Turn On or Keeps Shutting Off
  • Strange Noises or Clicking
  • Leaking or Dripping
  • Burning Smell or Discolored Water

Let’s break down each issue, what causes it, and how to solve it yourself—no plumber required for most fixes.

Step-by-Step Troubleshooting Guide

No Hot Water

  • Check Power: Make sure the breaker is on and the unit is plugged in. Test your outlet with another device if needed.
  • Reset the Heater: Turn the power off for 30 seconds, then restore. Look for a reset button or use the breaker.
  • Inspect Display/Panel: If you see an error code, note it for the next step.
  • Test Water Flow: Tankless heaters need a minimum flow to activate. Open multiple hot taps to see if it kicks in.
  • Check Inlet Filter: Sediment or debris can clog the water inlet screen, reducing or blocking flow. Clean or replace as needed.
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Flashing/Error Codes

  • Reference Your Manual: Every code means something different (ex: E5, E6, etc.). Look for a sticker on the panel or check the manual for meanings.
  • Common Codes: Temperature sensor, flow sensor, or overheating issues are frequent. Many are solved by cleaning, replacing a sensor, or descaling.
  • Clear the Error: Reset the unit after correcting the issue to clear the code. Persistent codes may require a replacement part (see below).

Low Water Flow or Temperature

  • Check Aerators and Shower Heads: Mineral buildup in faucets restricts flow. Soak and clean screens.
  • Inspect Inlet Filter: Again, sediment is a common culprit. Flush or replace the filter.
  • Descale the Heater: Hard water causes internal scale, which blocks flow and reduces temperature. Use a flush kit to clean out mineral buildup.
  • Adjust Temperature Setting: Make sure your digital display is set to your preferred temperature. Raise as needed, within safe limits.

Unit Won’t Turn On or Keeps Shutting Off

  • Verify Power: Double-check breakers and GFCI outlets. Power surges or outages may require a reset.
  • Overheating: Overheating trips a safety shut-off. Make sure inlet and outlet vents are clear and flush the heater if you suspect scale buildup.
  • Faulty Sensors: Temperature or flow sensors fail with age. Replace with genuine Rheem parts.

Strange Noises or Clicking

  • Normal Operation: Some clicking is normal as relays activate. Constant clicking or banging may mean scale buildup or a failing sensor.
  • Flush the System: Descaling can quiet most odd noises.

Leaking or Dripping

  • Tighten Connections: Check all water and electrical connections. Over time, vibration can loosen fittings.
  • Replace Worn Parts: Leaking around the heater itself may require new washers or O-rings—always use OEM or approved replacements.
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Burning Smell or Discolored Water

  • Burning Smell: Shut off power and check for debris or melted wiring. Do not use the heater until inspected if you suspect electrical problems.
  • Rusty or Brown Water: This is rare in tankless heaters but may indicate corroded plumbing upstream. Flush lines and consult a plumber if it persists.

Top Replacement Parts & Maintenance Kits for Rheem Tankless Water Heaters

Comparison Table

Name Key Features Specs/Capacity Price Link
Rheem RTEX-04 Heater Compact, efficient, digital controls 4 kW, 0.9 GPM, 240V View
Rheem Temp Sensor OEM, easy install, solves error codes Fits most Rheem RTEX models View
My PlumbingStuff Kit Flush pump, hoses, bucket, descaler 3.5 gal, 1/6 HP pump, reusable View

FAQ: Rheem Electric Tankless Water Heater Troubleshooting

  • How often should I descale my Rheem tankless water heater?
    Most homes should flush once a year. Hard water? Every 6 months is smart.
  • Why does my Rheem heater keep shutting off?
    This is usually a flow, power, or sensor issue. Check for clogged filters, low flow, or overheating. Reset the heater after any fix.
  • Can I replace parts myself?
    Yes, most basic parts (like sensors or filters) are simple to replace with standard tools. Always use OEM parts for safety.
  • My heater is making noise—is that bad?
    Some clicking is normal, but banging or gurgling often means it’s time to flush and descale.
  • When should I replace my Rheem heater?
    If repairs are frequent or your unit is 10–15 years old, a new model is more efficient and reliable.
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Conclusion

Rheem electric tankless water heaters are some of the most reliable on the market, but even the best need a little care. Most issues are quick fixes—just clean, reset, or swap out a sensor and you’re back to endless hot water. With regular maintenance and the right troubleshooting steps, you’ll enjoy years of comfort and lower bills. And if your heater is past its prime, now’s a great time to upgrade to a modern, more efficient model for worry-free hot water every day.

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