How to Dig Under a Concrete Floor for a Drain

Measure the diameter of your drain cover and the drainpipe that you need to place beneath the floor using a tape measure.

Add 6 inches to the diameter and then draw parallel lines along the concrete floor with a piece of chalk following the path that your pipe will take, including the location of the drain. Use the adjusted diameter as the width between the lines. Keep the lines straight by using a straightedge as a drawing guide, or alternatively snap a chalk line.

Wear a pair of safety goggles, a particle mask, work gloves and earplugs to protect you from injury while cutting through the concrete.

Place a jackhammer onto the concrete slab at the center of the space marked for the drain. Break through the concrete from the center point to the marked chalk outline using the jackhammer. Continue down the chalk line, tilting the jackhammer towards the opposing line to direct the broken edge of the concrete inward towards the trench you must create to install the pipe. Move the jackhammer over to the other line and repeat the breaking process along the second line, again tilting the jackhammer so that it cuts towards the interior of the trench.

Remove all of the concrete debris broken between the lines.

Dig the pipeline trench with a trench spade under the floor through the soil revealed by removing the concrete covering. Check with a building inspector to determine the necessary depth for pipes in your region. Dig the trench at the suggested depth plus an additional amount equal to the diameter of the pipe. Follow the open concrete, down the trench line and haul away the soil as you go to avoid its falling back into the trench.