Laying Sewer Pipe in Pavement Floors

Stretch the tape measure from a corner of the concrete forms or existing foundation wall to the location of the wall that will contains plumbing fixtures and requires drainpipes. Mark the location of the wall on the ground with marking paint. Move the opposite side of the structure's foundation and create a similar mark.

Tie the loose end of a roll of builder's twine to a brick and align the brick with the mark on the ground. Unravel the twine to the opposite mark, tie the twine to a second brick and align the brick with the remaining mark. The twine should run between the marks. Spray marking paint along the line to lay out the position of the wall that contains the plumbing on the ground. Lay out additional wall locations with the same procedure.

Dig trenches across the layout lines with a shovel or excavation equipment. Dig trenches to the depth required by your local building authority. In general, pipes must sit at least 12 inches below the underside of the slab. Note that trench depth varies according to climatic conditions, such as seasonal frost. Slope the trench toward the drainpipes' connection to the main sewer line; pipes must slope at least 1/4 inch per foot.

Set a builder's level on top of a straight piece of framing lumber. Place the framing lumber and level at the trench's bottom and use the level's bubble to gauge the trench's slope. Move dirt manually, with a shovel or excavation equipment to adjust the trench's slope. Tamp the bottom of the trench with a tamper to compact and further level the trench's bottom surface.

Check the location of the trenches relative to the concrete forms or foundation walls with a tape measure. Stretch builder's twine across the trenches' centers to indicate the desired position of the drainpipes, affix the line to bricks and set the bricks in a stable position on top of the forms or foundation.

Lay ABS drainpipes throughout the trenches' bottoms, cutting the pipes to size with a hack saw. Connect separate pipes with ABS drainpipe fittings. Connect the pipes and fittings without glue to check their locations; this process is called "dry-fitting." After confirming proper pipe placement, remove the dry-fitted components and clean burrs and impurities from the pipes' ends with emery cloth and a rag. Permanently assemble the pipes and fittings with ABS glue.

Wrap the portions of the pipes that will penetrate through the pavement slab with pipe wrap. Extend the pipe wrap at least 3 to 4 inches beyond the upper and lower faces of the slab. Affix the pipe wrap to the pipes with duct tape. Fill the trenches with dirt, compacting the back-fill material every 12 to 18 inches with a tamper. Pour concrete directly over the filled trenches and around the wrap-protected pipes.