Total
dissolved
solids
(mg/l)
A Temperature
(°C)
B Ca hardness
(ppm CaCO
3
)
C M-
Alkalinity
(ppm
CaCO
3
)
D
86 - 91 0.7 356 - 446 2.2 356 - 446 2.6
92 - 95 0.6 447 - 563 2.3 447 - 563 2.7
564 - 707 2.4 564 - 707 2.8
708 - 892 2.5 708 - 892 2.9
893 - 1000 2.6 893 - 1000 3.0
Interpretation of the values obtained:
• RSI < 6: boiler scale formation
• 6 < RSI < 7: neutral water
• RSI > 7: corrosive water
As a general rule, the RSI index should be between 5.6 and 7.5. If that is not the case,
contact a specialist.
5. Free chlorine (Cl
2
)
Disinfecting with chlorine is not done in closed systems, neither in energy recovery
systems.
A continuous level of 0.5 ppm should not be exceeded. For shock treatments, a maximum
limit of 2 ppm for maximum 30 minutes/day applies.
6.
Chlorides (Cl
-
)
Chloride ions will create pitting corrosion on stainless steel. Their concentration should be
limited, depending from the RSI value.
RSI < 5.5 5.6 < RSI < 6.2 6.3 < RSI < 6.8 6.9 < RSI < 7.5 7.6 < RSI
Cl
-
(ppm)
200 350 500 350 200
For energy recovery systems, the limit is 100 ppm.
7.
Sulphates (SO
4
2-
)
Sulphate (ppm)
Type of cooling system Standard Energy recovery
Single pass < 1000 < 200
Recirculating (with tower) < 1000 not applicable
Closed loop < 400 < 200
8. Iron and Manganese
Instruction book
2920 7109 51 123
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