[nomadking]

Originally Posted by danielf

Yes, plants love soapy water

Apparently many do.
Link

Question
Can I water my garden plants and vegetables with my used bath water?
Answer
Yes, you can water your plants with your bath water. It is a great way of helping your plants in the current drought conditions. In the last major drought in the UK, many gardeners found that using used bath water with bubble bath etc. created bumper crops because of the water containing high levels of phosphates. The only thing to remember is that if you live in a hard water area your acid loving plants such as azaleas will not be too keen on this water because of the high lime content.