Tree should be far away from the drain line. The roots will eventually grow into the pipe. Tree roots are incredible at finding water sources. Even a drop-at-a-time drip from a water pipe will be completely root wrapped in a few years.
Funny, that happened to a neighbor. There was this teeny crack in a pipe, and a tree root had squeezed into it then ballooned into this alien creature that blocked the drain in an attempt to suck out the water.
