Tar paper sewer pipe represents a specific era in underground construction, serving as a critical component for managing wastewater long before modern materials became standard. This felt-based product, saturated with asphalt, provided a waterproof barrier for drain lines, primarily in residential settings during the mid-20th century. Understanding its composition, installation method, and eventual failure is essential for property owners dealing with aging infrastructure.
Composition and Manufacturing Process
The core of tar paper sewer pipe is a heavy-weight felt mat, typically saturated with a penetrating asphalt binder. This asphalt provides the necessary flexibility and waterproofing qualities required for burial. A protective granular coating, often sand or a mineral aggregate, is applied to the outer surface to prevent the material from sticking during handling and installation. The primary function of this felt is to create a semi-permeable membrane that allows water to enter while keeping surrounding soil out, which helps maintain structural integrity until the pipe is installed.
Historical Use in Drainage Systems
Historically, this material was favored for its cost-effectiveness and ease of installation for gravity-fed sewer lines. It was commonly used for leach fields in septic drain systems and as interstitial pipe within gravel beds. The porous nature of the felt allowed effluent to seep out gradually, dispersing into the surrounding gravel soil. This method was popular in the 1950s and 60s, as it provided a reliable solution for rural properties where conventional sewer hookups were unavailable.
Installation Methodology
Proper installation of tar paper sewer pipe required meticulous preparation of the trench. The bottom needed to be compacted and leveled to ensure consistent bedding. The pipe was then laid with a slight pitch to facilitate the natural flow of liquids. Joints between sections were typically connected using a simple overlapping method, secured with additional asphalt or tar tape to prevent infiltration of soil at the seam. The pipe was then surrounded by a layer of clean gravel to facilitate drainage and provide structural support.
Common Failure Modes and Risks
Over time, the asphalt binder in tar paper sewer pipe degrades due to exposure to soil acids and fluctuating temperatures. This degradation causes the felt to become brittle and crumbly, leading to cracks and seam failures. Tree roots are particularly aggressive toward these materials, exploiting any weakness to infiltrate the line. When the matrix fails, the pipe can collapse, resulting in severe blockages and the need for immediate remediation.
Identifying Deterioration
Signs of failure are often visible during excavation or inspection. The felt may appear dusty or disintegrate when touched, indicating advanced aging. Soggy spots in the yard above the drain run can signal leaks, while lush vegetation might indicate consistent effluent seepage. Persistent backups in toilets or drains that are not caused by local clogs are a strong indicator that the underground pipe is no longer functioning correctly.
Modern Replacement Considerations
When a tar paper system fails, the standard solution is complete replacement with modern materials. PVC and ABS piping are the industry standards today, offering superior durability, joint integrity, and resistance to root intrusion. The removal process involves excavating the old line, which can be disruptive, and replacing it with the new polymer pipe. This upgrade ensures reliable wastewater transport for decades and eliminates the risk of future collapse associated with the organic felt material.
Comparison of Sewer Pipe Materials
While largely obsolete, comparing tar paper to modern alternatives highlights the evolution of drainage technology.
