Eight years ago, I had a bathroom and office installed downstairs. Along the way, they dug a trench through the existing concrete slab and put in the appropriate pvc drain. This "underslab" drain runs under my office. Now I want to find out exactly where this drain is located so that I can put in some (3) concrete anchor bolts in my office without drilling into the pvc drain. Is there an easy inexpensive way to locate this drain?

I am not a professional plumber, but a thought is a snake in drain and a metal detector.