How will you distinguish between soft water and hard water

Differentiating hard water from soft water —

1. Two unknown samples 'X' and 'Y' containing hard water and soft water are taken separately in a trough or beaker.
2. Ordinary soap is rubbed by the hands inside each sample.

Observation —

1. One sample of water 'X' lathers with soap
2. The sample of water 'Y' does not lather with soap.

Result —

1. The sample 'X' which lathers with soap is soft water.
2. The sample 'Y' which does not lather with soap is hard water.