After talking to my tutors they advised me to go with something a little less obvious than "save water".  So then I tried out "mind every drop" to get the message across.

To add some colour and emphasize the water I did the word 'drop' in red. My tutor then suggested to me that  I do the lock in red too to tie them together and with all the other stamps too. So from here I did the clothes peg, plaster and the zip all in red too.