Currently SLAMing the pool and backwashing into the backyard. I'm not concerned about the grass; the weeds took over long ago. But I am concerned about two 60-80 year old oak trees. Is highly chlorinated water (>=15 ppm) damaging to mature oak trees? For what it's worth, we've had heavy rains in the last month and I've been spraying fresh water into the backwash area to hopefully dilute the chlorine content.