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Laying of drains of the sanitary installation

Getting water to any room in the house can often be accomplished with very little planning, as long as there is a clear path between source and destination. Transporting water safely away from the destination and out of the house, on the other hand, requires a lot of planning. While water flowing into your home is pressurized and can be directed virtually anywhere, household drains rely on gravity and a constant slope to remove waste or excess water.

Determine the point where the fixture drain transitions from vertical to horizontal. For toilets, tubs and showers, this point is just below floor level. If you are installing a drain on a sink, mark the horizontal slope between the drain side of the trap and the vertical sewer pipe connected to your sewer system.

Mark the transition point with a pencil on an adjacent floor joist or structural member. For a sink drain, use the drain opening at the “P-trap” as the starting point.

Extend the mark from the starting point to the point where the drain line joins the existing sewer system. Use a spirit level for this purpose. Use this level line to determine a uniform slope along the entire length of the drain.

Determine the length of the drain pipe with a tape measure.

Mark the bottom of your pipe where the new drain joins the existing sewer system. This mark must be at or below the calculated slope. A greater slope, up to 1.25 cm, is acceptable.

Attach one end of the string to a floor joist or structural member near where the drain pipe becomes horizontal.
Trace the path of the drain pipe from the fitting to where it enters the sewer system. Use the string for this purpose.
Attach the end of the string to the mark indicating the bottom of the slope.

Use the string as a guide when laying the drain pipe. Matching the slope of the string and the newly laid pipe will ensure an even slope and good drainage.


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