If this water heater will be installed in an application where the supply water is hard, the water must
be treated with either the Noritz H2Flow or ScaleShield or a water softener. Refer to the below tables
for suggested treatment and maintenance measures to be taken based on the water hardness level.
Damage to the water heater as a result of water in excess of 12 gpg (200 mg/L) of hardness is not
covered by the Noritz America Limited Warranty.
Note: Water softeners may be regulated by the local water jurisdiction, consult with the manufacturer
for code, sizing, and installation guidelines; the below diagram is for reference only. For more
information about H2Flow and ScaleShield, contact Noritz America at 866-766-7489.
Residential Use Treatment Guidelines
Hardness
Type of Water
Level
0-1 gpg
Soft
(0-17 mg/L)
1-3 gpg
Slightly Hard
(17-51 mg/L)
3-7 gpg
Moderately
Hard
(51-120 mg/L)
7-10 gpg
Hard
(120-171 mg/L)
10-14 gpg
Very Hard
(171-239 mg/L)
Extremely
> 14 gpg
Hard
(> 239 mg/L)
* Install Noritz Isolation Valves to allow for flushing.
** Flushing is required if a water treatment device is not installed.
NORITZ
Tankless Gas
Water Heater
Pressure
Relief
Valve
Drain
Treatment
Flush
Device
Frequency*
None
None
None
None
H2Flow or
Once a Year**
ScaleShield
H2Flow or
Once a Year**
ScaleShield
Treatment
H2Flow
Required
Treatment
H2Flow
Required
Water Treatment System
Cold to Water
Heater
Shutoff Valve
Hot Water to Fixtures
Commercial Use Treatment Guidelines
Hardness
Type of Water
Level
0-1 gpg
Soft
(0-17 mg/L)
1-3 gpg
Slightly Hard
(17-51 mg/L)
3-7 gpg
Moderately
Hard
(51-120 mg/L)
7-10 gpg
Hard
(120-171 mg/L)
10-14 gpg
Very Hard
(171-239 mg/L)
> 14 gpg
Extremely
Hard
(> 239 mg/L)
* Install Noritz Isolation Valves to allow for flushing.
** Flushing is required if a water treatment device is not installed.
Shutoff Valve
Optional Sediment
Filter
Water Treatment Device
Treatment
Flush
Device
Frequency*
None
None
None
None
H2Flow
**
Once a Year
Suggested
H2Flow
**
Twice a Year
Suggested
Treatment
H2Flow
Required
Treatment
H2Flow
Required
City Water Supply
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