I've always done dtw with as little run off/waste as possible. The idea behind drain to waste is basic. You want to water just a little at a time. To where after your done and the roots are wet, there's maybe a 1-2TBS of run off. Then you let it dry and feed again. This method is best when you use clay pebbles. The more you can dry out and feed is the key here. When doing a proper drain to waste system, there is less waste than any other system. Just my 2 cents.