Introduction to Pipe Materials for Onsite Treatment Systems

Proper pipe selection and installation techniques ensure a watertight system

Introduction to Pipe Materials for Onsite Treatment Systems

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Piping is the conduit that collects wastewater from the source and conveys wastewater from one component to another. Piping transmits wastewater through the treatment and dispersal system. 

Building a wastewater conveyance system that is watertight and structurally sound begins by determining pressure requirements within the pipe, understanding the external loads on the pipe, and then selecting the appropriate pipe material for that site. Once the pipe material is selected, then proper installation techniques need to be followed to ensure long-term satisfactory performance of the conveyance system.

Common pipe materials

Ductile iron 

Ductile iron, also called ductile cast iron or nodular cast iron, is much less brittle than cast iron. Ductile iron pipe is stronger and easier to tap and requires less support compared to other pipe materials. In some instances, it may be appropriate or required to sleeve plastic pipe inside ductile iron for road and stream crossings.

High-density polyethylene 

The use of high-density polyethylene pipe is limited in onsite wastewater treatment system installations because of cost. It may be the appropriate material for installations requiring a flexible piping in inaccessible, unstable or shifting soil environments or where large temperature variations are expected. 

Another application is in high groundwater installations because there are fewer connections where leaking can occur. Other applications include trenchless installations like pipe bursting or horizontal direction drilling. It is commonly used at sites that require piping to be pulled through tunnels, under roads or structures. This material can be pulled in long assembled lengths using special installation equipment.

Acrylonitrile butadiene styrene 

Acrylonitrile butadiene styrene is a widely approved drain-waste-vent pipe material. This material is available in Schedule 40 dimensions as specified in ASTM D2661. This specification covers fittings and single and coextruded ABS plastic drain, waste and vent pipe made to Schedule 40 iron pipe sizes. ABS is usable for gravity-flow conditions, but it is not pressure rated.

Clay and Orangeburg 

Vitrified clay pipe (with a salt glazing applied to both the pipe's interior and exterior surfaces) was the material of choice for a lot of building sewers in the past. Orangeburg pipe is made from wood pulp and pitch. It was used from the 1860s through the 1970s, when it was replaced by PVC pipe. The name comes from the fact that most Orangeburg pipe was manufactured in Orangeburg, New York. Be careful handling Orangeburg pipe as it has often been treated with creosote to repel rodent and root invasion.

Polyvinyl chloride 

Polyvinyl chloride is the most common pipe material used in wastewater treatment systems. It is a plastic pipe used in both gravity and pressure applications. PVC has many advantages over other piping materials:

  • Light weight – half the weight of aluminum, one-fifth the weight of cast iron, and one-sixth the weight of steel. 
  • Low friction loss due to its smooth and seamless interior walls.
  • Requires no special tools to cut and can be installed by cementing, threading, gasketing or flanging. 
  • Ease of installation, resulting in lower installation costs.
  • Corrosion free, both internally and externally, and inert to attack by strong acids, alkalies, salt solutions, alcohols and many other chemicals. 
  • Self-extinguishing and does not support combustion. 
  • High tensile and impact strength that can withstand high pressure for a long period of time.
  • Low thermal conductivity factor compared to metal pipe. Therefore, piped fluids maintain a more constant temperature.   

Proper pipe selection and installation techniques ensure a watertight system. Watertight piping is important to both prevent leakage of untreated wastewater out of the system that might pollute groundwater and to prevent leakage of groundwater into the system that could overload downstream components. Pipe materials must withstand the internal and external forces required by the site conditions, must not pull apart in shifting soils, and not react with the wastewater or the surrounding soil.


About the author
Sara Heger, Ph.D., is a researcher and educator in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota, where she also earned her degrees in agricultural and biosystems engineering and water resource science. She presents at many local and national training events regarding the design, installation and management of septic systems and related research. Heger is the President-Elect of the National Onsite Wastewater Recycling Association and she serves on the NSF International Committee on Wastewater Treatment Systems. Ask Heger questions about septic system design, installation, maintenance and operation by sending an email to kim.peterson@colepublishing.com.



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