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Water & Sewer Laterals

Temporary Services  | Surveying and Layout | Excavation | Footings/Foundation  |  Foundation Options | Subrough Plumbing & HVAC | Dampproofing, Waterproofing and Window Wells>>Water and Sewer Laterals | Foundation Drain, Backfill and Rough Grade | Basement Slab

The water lateral is the pipe that runs from the city water supply into the house. The sewer lateral is the pipe that runs from the house to the city sewer pipe or to the septic tank

The supply pipe must be able to withstand high pressure and corrosion, both internally and externally. Flexible copper is probably the most common type of water lateral although plastic is used also. The water lateral is placed in a trench from the city water pipe to the house and is placed below the frost line to prevent freezing.

Modern Sewer lateral is pipe is made from plastic pipe, either ABS or PVC. Traditionally sewer lateral was made from clay, cast iron, concrete, or tar fiber pipe.

Installation process
For the sewer lateral , the pipe is placed in a trench dug with a shelf to one side (see illustration below). The pipe is hooked to the house sewer main and runs downhill to the city sewer main. The sewer lateral is installed with a "T" connection right before it hooks to the city pipe (this is used to plug the pipe for testing). As the pipe leaves the house a "Y" fitting and vertical pipe installed for a cleanout.
The sewer lateral is then filled with water to check for leaks and the test plug is pulled to make sure that it drains properly. The pipe is then covered with sand or pea gravel to protect it from breakage.

The water lateral hooks to the water supply and runs to the house. Before it actually goes into the house it runs through the water meter. In some areas there may not even be a water meter, or the water meter may be installed inside the house.
The installer drills a hole through the foundation ( or runs the supply under the footing into the basement or crawlspace portion of the house. A main shutoff valve is installed inside the house. In some areas the main shut off valve may be installed outside the house and accessible through a vertical pipe in the yard. The Yoke that holds the water meter usually has a shut off valve. The water lateral is pressurized or fill with water to test for leaks. After testing it is covered with sand or pea grave for protection.

Typically the water and sewer laterals are installed by excavators or plumbers. A sewer cleanout is installed next to the house on the exterior. The cleanout is a "Y" fitting that is attached to the main line to allow the line to be unblocked. Check with the city water and sewer dept about the location of the cleanout. The water supply is also installed at the same time as the sewer lateral. A trench is dug for the sewer and the water lateral is placed above the sewer on the trench.

Both the water and sewer laterals are estimated by the lineal foot.

Notes to the owner-builder
Savings can be made by placing both laterals in the same trench. It is common practice and saves money to schedule the laterals as part of the backfilling process if the same subcontractor is doing both the excavation and laterals.
The lateral inspection will vary depending on where you live. In some areas the building department will inspect, and in others the water utilities will be in charge. Some jurisdictions require that the water and sewer are water tested, and others don't. Most of the time, installers know the local codes and procedures for inspections. Contact your local building department and water utilities for local requirements.


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