Measure out the detergent based on the instructions for soft water. You do not need to use water softener or softening salts for the washing machines.
The household water in the Helsinki Metropolitan Area is soft, which means that its lime content is low. This is why less detergent can be used than with hard water.
In the Helsinki Metropolitan Area, the hardness of water ranges from 3.0 to 4.5 dH, depending on the plant.
Degree of water hardness
Very soft = 0-2 °dH
Soft = 2-5 °dH
Medium hard = 5-10 °dH
Hard = 10-21 °dH