Specifications for Installing Sewer Lines

Pipes and Fittings

• Generally, sewer pipe and fittings for residential installations consist of Polyvinyl Chloride (PVC) or cast iron. The main residential sewer pipe diameters vary from 4 to 6 inches. Branch lines must be 1-1/4 to 2 inches in diameter. Pipes and fittings must meet or exceed specific standards, such as those outlined by ASTM International, which establishes voluntary standards for materials systems and services. Many codes require the pipe manufacturer to mark materials with the manufacturer's name or trademark and production code.

Permit and Buried Lines

• Typically, the plumbing contractor must obtain a work permit before proceeding with the project. The contractor must also erect guards, rails, lights or other equipment, when excavating, to protect workers and the public when excavating to lay pipe. Most municipalities require the contractor to contact the city before excavating in order to locate and identify water,steam, gas, utility or other buried lines.

Service Check Valve Installation

• Most codes require a service check valve installed in the sewer line. The service check valve allows waste water to flow toward the main sewage line but prevents waste water from reversing back toward the building. The valve must have certain components that permit access to parts of the valve. The valve has to meet other requirements as specified by building codes and ASTM International.

Excavation and Installation

• When excavating, remove only as much soil as necessary to stay ahead of the workers laying the pipe. This provides protection against having an open trench in case of rain or a delay in the project. Dig the trench manually or use a backhoe. Start digging from the foundation wall of the house. Make the width of the trench about 24 inches. This ensures enough room to work when laying the sewer pipe. Follow the local building code rules to prepare the soil surface. Lay the pipe on a solid bed to prevent the soil from settling and causing the pipe to move. Make connections according to the guidelines for the material selected. PVC pipe and fittings usually require special PVC cement to make the connections. Keep the pipes as straight as possible for better waste water flow. In addition, local rules require a specific slope for sewer pipe, such as a 1/4-inch slope for each foot of pipe installed.

Connection to Public System or Septic Tank

• When connecting to a public system, the municipality usually requires the work to take place under the direct supervision of a plumbing supervisor from the building inspection department. The main sewer lines are about 10 feet below the street surface. The house sewer line usually connects to the main sewer at a 45-degree angle located at a point above the main line. Follow the manufacturer's instructions for connecting the pipe to a septic tank; have the sewer pipes and connections inspected and approved by the building code inspector before fully covering the line.