Seattle Public Utilities Mami Hara, General Manager/CEO

Sagging Pipes

Side sewers are constructed at a slight slope of ¼ inch per one foot of pipe. This slight slope allows for wastewater to take advantage of gravity’s force and move debris through the pipe. Sags are typically only a problem if they are severe enough to cause debris to settle and collect in the pipe. Settling debris may eventually result in sewer backups.

Recommendation

No repair

sagMinorSideSewer

Minor Sag.

Minor buildup of debris may occur, but typically not enough to cause negative effects on the sewer. Sags are considered minor if it is less than 25% of the pipe diameter.

Routine inspection

sagModerateSideSewer

Moderate Sag.

A sag 25 to 50% of the pipe diameter would typically cause debris to settle in the pipe which may eventually cause a backup.

Inspect every two to five years.

Repair

sagSevereSideSewer

Severe Sag.

A sag that is 50% or more of the pipe diameter has a higher likelihood for buildup of debris, which may cause a backup over time.