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Rinnai Smart Cylinders low-medium pressure indoor stainless steel: Owner and installer guide: 20432-A 01-15
Water quality
Rinnai water heaters are manufactured to suit most NZ council water
supplies. However some water supplies can have a detrimental effect
on the water heater, its operation, and life expectancy.
Pitting corrosion
Rinnai stainless steel tanks are made from 2101 grade duplex stainless steel. This material has
very good resistance to pitting corrosion with a Pitting Resistance Equivalent Number (PREN)
of 26. This is a commonly used engineering indicator of corrosion resistance in stainless steel
materials. The higher the PREN number the greater the resistance. In comparison 304 grade
stainless, which is commonly used in domestic cookware and kitchen sinks, has a PREN number
of 19. This means that Rinnai stainless steel tanks are highly resistant to pitting corrosion, but not
completely immune from it.
Pitting corrosion may occur in the form of deposit attack if the water supply has a high
percentage of dissolved solids present. It is advised in areas with a high concentration of
dissolved solids in the water supply that consultation with water quality and filtration experts be
undertaken.
Hard water
Hard water (containing calcium carbonate) can cause scaling on hot surfaces. We recommend
a water temperature of no more than 65 °C to minimise scale build-up. Scale reducing or water
softening devices should be considered in hard water areas. The unit is not guaranteed against
damage due to scaling.
Water quality outside the limits (as set down below) will void this warranty. Water quality tests
must be carried out at the customer’s own cost but Rinnai will reimburse any reasonable test
costs where water quality is within the limits tabled.
Water Quality and Impurity Limits
TDS (Total Dissolved Solids) Total Hardness CaCO
3
Dissolved (free) CO
3
pH
Langelier Index
Up to 600 mg/L or ppm
Up to 200 mg/L or ppm
Up to 25 mg/L or ppm 6.5-8.5 Between -1.0-0.8
Most metropolitan water supplies fall within these limits. If you are unsure about water quality,
please contact Rinnai and we will provide you with the details of an authorised agency able to
test your water for compliance to Rinnai standards. If sludge or foreign matter is present in the
water supply, a suitable filter should be incorporated in the water supply.
Some examples of water quality issues where water may need to be treated:
• Hard water (areas including Wanganui)
• Aggressive water (areas including Christchurch)
• Both hard and aggressive water (some bore water)
