I've never used the waste water either. I really should, but have never worked out any working logistics. What I should do is fill up a barrel with water outside, and run soaker hose to the foundation from the barrel. I just don't know how I would install the bulkheads, how to keep the mosquitos out of the barrel of water (even a puddle can be an issue here) and how to keep insects (ants, for example) from plugging up the drain line by trying to set up home in the outlet.
Also, I don't know if water would exit the soaker hose if the barrel didn't have a significant volume of water to create pressure. Once it gets down to a couple of inches, it might sit there and stagnate. :?: