DETERMINING THE CONDITION - With the use of televised inspection, the structural condition of sanitary sewers can be examined. These examinations are frequently used as a basis to make restoration decisions. To assist in making these important and costly decisions, it should be recognized that the greatest threat to extended system performance results from a change in one of the following factors:

1. The Load on the Pipe - The load on a pipe approaches a maximum level when the trench backfill soil reaches optimum consolidation. The load does not normally change significantly after backfill consolidation unless the trench conditions change.
2. The Strength of the Pipe - The strength of clay pipe is retained due to its ceramic qualities and chemical inertness. Clay pipe can be damaged by impact or point loading but, when properly installed in accordance with ASTM requirements, clay pipe can provide extended service life.
3. The Pipe Embedment - Improper installation or a shift in embedment resulting in pipe movement is the major cause of distress to clay pipe. If no embedment movement or migration occurs, a clay pipe line is very likely to remain in a serviceable condition both structurally and hydraulically. 

POINTS TO CONSIDER - Repairing and replacing existing lines is a costly undertaking and an agency should consider all factors when making a restoration decision.

1. Relining may not be a long term solution and short term benefits are not always fully realized. For example, it does not correct misalignment or major structural defects.
2. Structural and alignment conditions that are revealed by the investigation probably occurred at or near the time of installation.
3. A localized area of distress may have been caused by post installation construction of another utility above or near the original sewer installation.
4. Restoring the mainline is only a partial remedy. Lateral sewers must also be considered in a total rehabilitation program as they contribute to a major portion of the infiltration. Restoring the mainline may “shift” the point of infiltration to the lateral sewer with only a partial reduction of the total infiltration.
5. Lines which have illegal or improperly installed lateral connections or root intrusion, need to be remedied and measures taken to prevent a reoccurrence of the problem.
6. No lining, coating or other pipe material has been demonstrated to last as long as vitrified clay pipe.

GUIDELINES FOR MAKING RESTORATION DECISIONS - There are different degrees of problems observed. Experience suggests the following for restoring vitrified clay pipe lines:

1. Lines with little or no infiltration or potential for exfiltration and show no visible evidence of embedment migration need no immediate response even though there may be minor structural distress observed. These problems probably relate to the original installation and the present condition may not have changed significantly since that time. The pipe should be monitored for change and may be repaired in a routine cost effective manner.
2. Lines which have a visible stream of water entering the system or minor structural distress but show no evidence of embedment migration should be corrected as soon as practical.
3. Lines which demonstrate significant infiltration, embedment material migration and structural damage should receive the highest priority for repair or replacement.

CONCLUSION - An agency should always consider point repair or replacement with modern clay pipe with compression joints which will provide a long-term solution.