How do I locate rough plumbing under basement floor?

Question

I am in the process of finishing my basement. I purchased the house 3 yrs ago as a spec home. I was told by the builder that the basement was "rough plumbed" for a bathroom, but he had a "thin layer" of concrete poured over the plumbing in the event that the purchaser did not want to put in a bathroom. The builder marked the floor with a marker where he said the pipes for the toilet, tub, and sink would be at. I have drilled several holes with a masonry bit, chipped the concrete away down approximately 1", and I can not locate where the pipes are. Any idea how I can locate the pipes?

Answer 1

Hmmm.  Ok, for every drain there should be a vent.  If you have a 3 piece rough-in bathroom in your basement you should be able to see at least 2 vent pipes running vertical from the floor between studs up from the floor, unless your wall studs are covered by drywall.

If you are in the process of finishing your basement & have covered the walls where your bathroom should be, you need to uncover those walls.  Then, trace the vertical vent pipes which probably serve your bathroom down to a point where they meet the floor.  

Your basin shouldn't have a dedicated vent because it's wet venting your toilet, so forget about that.  But, your toilet  should be 12 1/2" from the rear wall stud & it's serving vent is probably 2" wide.

Your basin drain should be sticking out a few inches from the vertical wall about 18" from the floor.

Your tub should be 14 1/2" away from the closest wall stud apendicular to it (if you live in Canada).

If there is no framing in your basement & you see no vent pipes running vertical between studs where you bathroom should be, consider that, your builder was mistaken about there being, "rough plumbing."

Hope this helps.  Each one teach one.