LC Minor Easy DIY

Rinnai Tankless Water Heater LC — Scale Buildup / Descale Reminder

Rinnai Tankless Water Heater · Error code LC

What LC Means

LC (Lime/Calcium) indicates scale buildup in the heat exchanger. Unit may still operate but performance is degrading.

Symptoms

  • LC or LC0-LC9 on display
  • Lower hot water output
  • Temperature swings

Common Causes

1
Hard water deposits in heat exchanger

Calcium scale insulating tubes.

2
No prior descale maintenance

Recommended yearly with hard water.

3
No softener / scale inhibitor

Untreated supply water.

How to Fix It

  1. Schedule a descale with vinegar or manufacturer-approved tankless descaler.
  2. Use isolation/service valves with a submersible pump — circulate 60-90 minutes.
  3. Clean the inlet water filter screen.
  4. After descale, reset the LC counter per service manual.
  5. Install a softener or scale-prevention device to extend service intervals.

Parts You May Need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

Common replacement Tankless descaling kit View on Amazon→ Common replacement Service valve kit View on Amazon→

More Rinnai Tankless Water Heater Codes

02 02 — Power Interruption / Memory Loss 03 03 — Loss of Communication / EZConnect Issue 10 10 — Air Supply or Exhaust Blockage 11 11 — No Ignition 12 12 — Flame Failure 14 14 — Thermal Fuse / Overheat Cutoff

All Rinnai codes → All tankless water heater codes →

Verified against manufacturer documentation: rinnai.us

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.