Automated irragation
 

Hello

I hoping someone can help me. We've got a little courtyard with raised beds. It's so small I thought it'd be great if we could divert all the lovely rain water from the roof on it's way down to earth. I'm intending to install a water butt to the down pipe. My question is: would it be possible to supply a timed irrigation system from the butt which switched to the mains if the water ran out?

Just had a brainwave... Would it be possible to top up the water butt from the mains?