Question
do i need to worry about a newly planted corkscreww willow tree roots damaging my septic tank piping or septic drain field pipes?

Answer
Willows like water and the roots are fibrous and will seek water. Do not plant it near a septic tank or septic lines. The roots will enter these lines and clog them. The newer type PVC sewer lines are sealed and the roots can not get into them. The roots are fine around walkways and drive and foundations. Plant at least 25-30 feet from any septic lines.