Seattle Public Utilities Mami Hara, General Manager/CEO

Offset Joints

Offset joints can potentially lead to sewer backups and sink holes. Side sewers are constructed by using several segments of pipes connected together by joints. If the joints do not perfectly match up, soil and debris can build up and eventually lead to sewer backups.

If the offset joints are exposed, the soil around the pipe can erode and wash away, leading to empty space around the pipes. The empty space around the pipes can be instable and eventually lead to sink holes. Here are different examples of offset joints and recommendations for repair.

Recommendation

No repair

offsetMinorSideSewer

Minor offset joint.

Buildup of debris is unlikely to cause any negative effects on the sewer system.

Routine inspection

offsetModerateSidSewer

Moderate offset joint

Moderate offset joints cause some debris buildup. Typically would not cause a backup since there is no exposed soil around the joint.

Inspect after a few years. If no change, no repair is necessary.

Repair

offsetSevereSideSewer

Severe offset joint

Surrounding soil may erode into the pipe and lead to voids and cause a backup.

Severe offset joints should be repaired.