I have a revolving barrel compost unit, can the the dark coloured liquid that drips from the unit be used to feed plants, if so should it be diluted?

Hi Paula, the dark liquid from your compost is likely to be leachate which isn't suitable for putting on the garden. If there is liquid coming out of your tumbler then it is too wet which means the compost will not break down properly. Add dry matter such as shredded newspaper, cardboard, pea or barley straw and mix it into the compost well.  Lianne.