Navien Error Code 041 — Causes & Fix

Code 041 (or E041) = Condensate drain blocked. Condensing models only. The unit detected condensate level rising in the trap and shut down to prevent overflow into the burner area.

Where condensate goes (normal)

1. Heat exchanger creates acidic condensate as combustion byproduct (1-2 gallons/day)
2. Drips into the trap at the bottom of the cabinet
3. Routes through a ½" PVC drain line
4. Discharges to floor drain, sink trap, or condensate pump
5. Neutralizer required if running to iron drain pipe or septic (acidic pH 3-5 needs neutralizing)

Diagnostic sequence

1. Condensate pump (if installed)

If your install uses a condensate pump (no gravity drain available), the pump may have failed. Listen for it cycling. Silent during recent draw = dead pump. Replace ($50-100).

2. Drain line freeze

If the drain line runs through an unconditioned space, winter can freeze it. Visible ice or frost confirms. Insulate and add heat-trace cable.

3. Drain line sediment

Condensate carries minerals; over years it deposits scale inside the drain line. Disconnect, inspect, and clear. Replace if heavily occluded.

4. Condensate trap blocked

The trap itself can accumulate sediment. Remove, inspect, clear. Photograph before disassembly to confirm orientation on reassembly.

5. Neutralizer media exhausted

If you have a neutralizer cartridge, the calcium carbonate media is consumed over 1-2 years. When depleted, the cartridge restricts flow. Replace media.

Reset procedure

1. Identify and clear the blockage
2. Verify free flow by pouring water into the trap inlet
3. Power cycle the unit
4. Monitor for normal operation

If you have Code 012 too

041 + 012 together = blockage caused enough backup to disrupt flame detection. Same underlying fix.

Prevention

• Annual trap inspection (in our maintenance checklist)
• Insulate drain lines through unconditioned spaces
• Replace neutralizer media every 12-18 months
• Verify drain line slope (¼" per foot minimum)

Bottom line

Code 041 is purely mechanical — find the blockage and clear it. Almost never a sensor or PCB issue.