How to Find a Preexisting Rough-In Located under the Floor Tile in the Basement

Remodeling a basement to add a toilet, shower or sink can be a challenge, but if some of the work has already been done for you, the task is less daunting. Some builders will rough in and plug the plumbing for such future additions as an early step in basement construction, then cover access to it with tile flooring. If you locate the concealed rough-in before you plan the location for basement bathroom fixtures, you can avoid installing new lines. Knowing how plumbing codes affect standard sizes and locations for rough-ins will aid your search.

Home blueprints
Hammer
Measuring tape
Masking tape

Instructions

- 1
  Look for the original blueprints for your house. The locations of the plumbing rough-ins will be marked, making it easier to find them in the basement.
- 2
  Look at the overhead pipes in the basement that vent and drain plumbing fixtures on the floor above. Look for a cap in the side of one of the pipes that indicates it is ready to have the vent from a basement tub or shower installed.
- 3
  Tap gently on the basement floor tile directly below this cap to search for the location of the waste rough-in for the shower or bath. Listen for a hollow sound that would indicate that a hole under the tile for a 12-inch-square shower or tub drain.
- 4
  Look in the walls for a 2-inch vent stack installed in the wall for a sink vent and drain.
- 5
  Knock on the floor around the sink vent to find the toilet rough-in. The floor in the correct location will sound different when you tap it.
- 6
  Start tapping at 12 1/2 inches from the wall to find the 4-inch drain hole for the toilet.
- 7
  Mark the locations of the rough-ins with masking tape placed on top of the tile.

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