Need more explanation or a picture ot understand what you are talking about. Are you talking rusty water? Coming up from the drain? water coming up from a drain, rusty or not implies a clog. If it's a rust stain, somebody could have used steel screws where stainless steel or brass is called for. If your drain lines are cast iron, and several other types used years ago, they can leak at a joint. A leaking joint will attact tree roots. You can usually get a drain cleaner out to rout out the line, but it won't fix the leak. The alternative is live with it and have the line cleaned periodicall, or replace it. Cutting a tree down may not stop if for awhile, since the roots will live on for awhile. There are things you can put down the drain to slow the roots regrowth, if it is that. The long-term answer is a new drain line with sealed joints so there are no leaks.