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The test water for measuring and adjusting the water
hardness can be drawn off at a draw-off point down-
stream of the water softener. Prior to draw off water,
ensure that the blended water, which has undergone
a new adjustment has flown through a possibly long
pipe from the water softener to the draw-off point. For
a correct comparison of the measured values, the test
water should be drawn off at normal flow rate (1 draw-
off point fully opened) without simultaneously consu-
ming water at another spot.
According to the German water quality regulations
(TrinkwV) from 01.01.2003, the limit value for sodium
in potable water is 200 mg/l. This value does not apply
to mineral and table waters, which sometimes contain
more than 1.000 mg of sodium per litre.
The table below "Calculation of the sodium content"
allows to determine whether the blended water is still
in compliance with this maximum value of the sodium
content.
When the calculated total sodium content exceeds the
admissible value of 200 mg/l, adjust the setting of the
blended water hardness to a higher value.
Table 1: Calculation of the sodium content
Calculation of the sodium content
° dH
Raw water hardness (ask water operator or
measure with hardness measuring device)
- ° dH
Hardness of blended water (measured value)
= ° dH
Reduction of the water hardness
x 8,2
mg Na/°dH Sodium-ion exchange value
= mg/l
Increase of the sodium content due to softe-
ning
+ mg/l
Sodium already present in the raw water (ask
water operator)
= mg/l
Total sodium content in the blended water
Table 2: Example: calculation of the sodium content
Example: calculation of the sodium content
20 ° dH
Raw water hardness
- 8 ° dH
Hardness of blended water
12 ° dH
Reduction of the water hardness
x 8,2
98 mg/l
by softening
10 mg/l
from water operator
108 mg/l
Total sodium content in the blended water
