AMERICAN Ductile Iron Pipe
ANSI/AWWA C150/A21.50
and
ANSI/AWWA C151/A21.51
Standard Laying Conditions

Flat-bottom trench.† Loose backfill.

Flat-bottom trench.† Backfill lightly consolidated to centerline of pipe.

Pipe bedded in 4" minimum loose soil.†† Backfill lightly consolidated to top of pipe.

Pipe bedded in sand, gravel or crushed stone to depth of 1/8 pipe diameter, 4" minimum. Backfill compacted to top of pipe. (Approximately 80% Standard Proctor, AASHTO T-99.)

Pipe bedded to its centerline in compacted granular§ material, 4" minimum under pipe. Compacted granular or select material†† to top of pipe. (Approximately 90% Standard Proctor, AASHTO T-99.)

*For 14" and larger pipe, consideration should be given to the use of laying conditions other than Type 1.
†"Flat-bottom" is defined as undisturbed earth.
††"Loose soil" or "select material" is defined as native soil excavated from the trench, free of rocks, foreign material and frozen earth.
§ Granular materials are defined per the AASHTO Soil Classification System (ASTM D3282) or the Unified Soil Classification System (ASTM D2487), with the exception that gravel bedding/backfill adjacent to the pipe is limited to 2" maximum particle size per ANSI/AWWA C600.