Navien Water quality limits and flushing schedule
Navien Water quality limits and flushing schedule: reference table for the tankless water heater (Navien NPE-2 series): a quick-reference table with notes.
Navien Water quality limits and flushing schedule table
| Hardness | grains/gal (mg/L) | Treatment | Flush frequency |
|---|---|---|---|
| Soft | 0-4 (0-60) | None | None |
| Moderately hard | 4-7 (61-120) | None required | Once a year |
| Hard | 7-9 (121-160) | Softener or Navien PeakFlow recommended | Once a year |
| Very hard | 9-12 (161-200) | Softener or PeakFlow highly recommended | Residential once a year; commercial twice a year |
| Extremely hard | >12 (200) | Softener or PeakFlow required | - |
How to use the Navien Water quality limits and flushing schedule table
Find your exact model in the first column and read across the row. Values in the Navien Water quality limits and flushing schedule table are a summary for quick reference; the rating plate on the unit and the manufacturer's manual for your model always decide. If your model is not listed, or a value looks different from what you see on the unit, check the manual before changing anything.
Notes
- Other max levels: hardness 200 mg/L, chloride 250, copper 1.0, iron 0.3, manganese 0.05, sulfate 250, TDS 500, zinc 5, chlorine 4 mg/L; aluminum 0.05-0.2 mg/L; pH 6.5-8.5.
- Flushing is advised when no treatment device is installed; use white vinegar or a tankless descaler.
- Damage from poor water quality is not covered by warranty.
- Manual's flush column for moderately hard to hard rows is merged - read as once a year.
Applies to: Navien NPE-A2 (built-in recirculation) and NPE-S2 condensing tankless water heaters: NPE-150S2, NPE-180A2/S2, NPE-210A2/S2, NPE-240A2/S2
Navien models this applies to
NPE-150S2NPE-180A2NPE-180S2NPE-210A2NPE-210S2NPE-240A2NPE-240S2
Navien Tankless Water Heater error codes →
Source: Navien NPE-A2/S2 Installation Manual, 3.1 About Water Quality, p.15. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.