Generally, the roots have a lawful right to be there; Except. if the tree was planted after the pool or other object being injured, damaged, or destroyed. A tree can not be liable, and in many cases is offered protection by city bylaws. On the other hand the pool owner has a right to quiet and undisturbed enjoyment of his/her land, In conclusion the reasonability of both cause and remedy, if not settled by the parties, must be settled by a Judge in Civil Court. The only case where a homeowner can take action against roots, is when they create a blockage to the essential services of the home. ie water, sewer, electric. Advice: if no cooperation by parties. 1.Forget it,2. move, 3. put aside lots of $$ and pray for luck in Court, or the other party being poorer.