Common sewer pipe materials and their characteristics
Vitrified clay pipe (VCP)
Vitrified Clay pipe is made from a blend of clay and shale that has been subjected to high temperature to achieve vitrification, a process which results in a hard, inert ceramic pipe. Clay pipes typically last for 50 to 60 years. Terracotta, a type of clay pipe, is a clay-based unglazed or glazed ceramic, where the fired body is porous which is a very common pipe in sanitary sewer piping prior to 1940.
Pros: Clay pipe is chemical resistant and has a fairly long life span.
Cons: Clay pipe is difficult to install, is brittle (subject to cracking) and the joints are subject to root intrusion as well as inflow and infiltration.
Root Intrusion Inflow/Infiltration
Cast iron pipe has been a sewer line mainstay for decades and has an average lifespan of 30 to 50 years. Over time however, in this moist environment, rusting and corrosion naturally set in. As these problems progress, the pipe is weakened and eventually needs to be replaced due to advanced deterioration or failure.
The real danger for cast iron pipes is corrosion. Over time, wastewater flow will etch a channel at the bottom of the pipe that - if left untreated - will erode through the pipe and weaken the pipe structure and allow for foreign material to enter the line. At the same time, wastewater can escape the pipe causing erosion and eventual bellies in the line that will lead to catastrophic collapse.
Failed Cast Iron Pipe
The Fibre Conduit Company was changed to the Orangeburg Manufacturing Company in 1948. The post-war housing building boom was well underway, and the types of pipe then available ( and affordable) for sewer and drains were limited. A heavier walled version of the fibre conduit was developed and sold as "Orangeburg" pipe (in sizes ranging from 2" to 18" I. D.) for sewer and drain applications. The joints were made with couplings of similar material -- utilizing no gaskets, joint sealant, etc., just simple compression, making the pipe potentially susceptible to I/I and/or root intrusion. The pipe was lightweight (but brittle), and it could be cut by hand with carpenter saws. It was recognized early on that fibre conduit pipe had a tendency to deform when subjected to concentrated pressures over long periods of time. Orangeburg pipe was commonly used from 1948 into the 1970’s.
Orangeburg pipe is almost impossible to maintain because of its material makeup. When roots intrude into the pipe, the mechanical rooter tears out pieces of pipe while it cleans, leading to collapse as well as collapsing from age.
Cross Section of failed Orangeburg Pipe
Polyvinyl Chloride Pipe (PVC)
PVC pipes are versatile, flexible, and one of the more affordable and popular sewer pipe options. The pipe is resistant to chemical damage and corrosion. PVC piping is lightweight and easy to cut into segments, which makes this some of the easiest piping to install. Properly glued, PVC is watertight and impervious to roots at the joints.
The only significant problem with PVC is that it can't support as much weight as cast-iron or clay. But that should only be a problem if the pipe is under an area with heavy vehicular traffic. Installation is usually by conventional trenching, disturbing landscaping hardscaped areas when replacing older defective pipe materials (orangeburg, cast iron or VCP).
Typical PVC Sewer Lateral
Acrylonitrile Butadiene Styrene (ABS)
Very similar characteristics to PVC pipe. Easy to work with, impervious to roots and watertight at the joints when glued properly. A little less forgiving during installation. ABS is not often used for sewer laterals although an acceptable material.
Typical ABS Sewer Lateral
High Density Polyethylene pipe (HDPE)
High Density Polyethylene pipe (HDPE) is currently the most common type of piping used for sewer lateral replacement. It characteristics lend itself well to sewer laterals because it is strong, semi flexible and has no mechanical or glued joints (it is heat welded) for a watertight and root impervious lateral. It is also chemical resistant and very resistant to breakage.
The usual method for installation is “trenchless” technology where a cable is fished through your old lateral and a bursting head breaks away your old lateral. A pit is dug at the exterior of your house and at the city main. A new one-piece HDPE pipe is pulled behind the bursting head and is installed simultaneously. The disturbance to the landscape/hardscape is kept to a minimum.
Typical HDPE Lateral Installation
Diagram showing the process for trenchless lateral replacement