HI lizp,
are these planters on their own seperate zones, or are they connected to a lawn/shrub zone? Just that there may be other solutions other than adding drainage to your planters.

Blustrat
I wish I was better at posting pix ! Took pix with the digital camera recently...They are oversized boxes located up on my porch. (We have an old house in historic Dallas which is pier and beam and is several feet up). I do have an irrigation system for lawn and beds, yet I have to hand water all my pots and these newly constructed boxes.
What were ya thinkin'? :)
liz

lizp,

Yeah, you can use solid drip tubing to get your runoff water down to your garden. Your local irrigation supply store should stock it. When I worked at a supply store we sold it in 50 foot lengths.
It should be an easy product, and the tubing is pretty inexpensive.