Vitrified clay pipes are composed of crushed and blended clay that are formed into pipes, then dried and fired in a succession of temperatures. The final firing gives the pipes a glassy finish. Vitrified clay pipes have been used for hundreds of years and are strong, resistant to chemical corrosion, internal abrasion, and external chemical attack. They are also heat resistant. These pipes have an increased risk of failure when mortar is used in joints because mortar is more susceptible to chemical attack than the clay. Other types of joints are more chemically stable. It has been shown that the thermal expansion of vitrified clay pipes less than many other types.

The applicability of different pipe materials varies with each site and the system requirements. The pipe material must be compatible with the soil and groundwater chemistry. The pipe material also must be compatible with the soil structure and topography of the site, which affects the pipe location and depth, the supports necessary for the pipe fill material, and the required strength of the pipe material.

The following list shows background information to be used in determining what type of pipe best fits a particular situation:

• Maximum pressure conditions (force mains)
• Overburden, dynamic, and static loading
• Lengths of pipe available
• Soil conditions, soil chemistry, water table, stability
• Joining materials required
• Installation equipment required
• Chemical and physical properties of the wastewater
• Joint tightness/thrust control
• Size range requirements
• Field and shop fabrication considerations
• Compatibility with existing systems
• Manholes, pits, sumps, and other required structures to be included
• Valves (number, size, and cost)
• Corrosion/cathodic protection requirements
• Maintenance requirements

The advantages and disadvantages for specific pipe materials are listed below. The primary advantages and disadvantages to consider for pipes used in sewer applications include those that are related to construction requirements, pressure requirements (force mains), depth of cover, and cost.

Ductile Iron
Advantages:
* Good corrosion resistance
* High strength
Disadvantages:
* Heavy

Concrete
Advantages:
* Good corrosion resistance
* Widespread availability
* High strength
* Good load support capacity
Disadvantages:
* Requires careful installation
* Heavy
* Not hydrogen sulfide (H2S) resistant

Vitrified Clay
Advantages:
* Resistant to acids and most chemicals
* Strong
Disadvantages:
* Joints susceptible to chemical attack
* Brittle, may crack, careful installations
* Short joints and many joints make it prone to infiltration

Thermoplastics (PVC, PE, HDPE, ABS)
Advantages:
* Very lightweight
* Easy to install
* Economical
* Good corrosion resistance
* Smooth surface reduces friction losses
* Long pipe sections reduce infiltration potential
* Flexible
Disadvantages:
* Susceptible to chemical attack, particularly by solvents
* Strength affected by sunlight unless UV protected
* Requires special bedding

Thermosets (FRP)
Advantages:
* Corrosion Resistant
* High strength
* Lightweight
Disadvantages:
* High installation cost
* High material cost
* Brittle (may crack): requires careful installation