It's a hot summer day and the sun is bright—perfect weather for taking a dip in your pool. You venture out to the backyard to check out the pool you haven't used since last summer. Lo and behold, it's ...

Q: I got home from work last night and couldn’t wait to get into my pool to soak away the day, but when I got to the backyard, the pool water was green—not light green, either, but dark. I didn’t even ...