Question
I live in the Inland Northwest, in Washington State, in a neighborhood where each house in on a 1/4 acre square lot.  Our next door neighbors have a 7-year old willow tree in their back yard which is planted approximately in the center of their property lines.  We have an inground pool on our property that extends to approximately 6 feet to the edge of the fence, which is the property line of our neighbors and us.  My guess is that makes the willow tree trunk about 50 or so feet from our pool.

My question:  Is the root system of this tree going to grow into our pool and yard resulting in damage to our sprinkler system and, more importantly, pool system? If so, what course of action should I take?

Answer
The roots spread about 1 1/2 time the width of the branches. So a willow 50 feet from the poll should not be a problem. The roots tend to seek water and IF there is a leak in a pipe this would be how the roots enter. They will not harm the sprinkler system or will not penetrate the pool lining. That far away I do not think you will have a problem.