IS 783 provides comprehensive guidelines for the handling, trench excavation, bedding, laying, jointing, and backfilling of precast concrete pipes. It is primarily used by civil and public health engineers to ensure underground drainage, sewerage, and water supply networks are installed correctly to withstand soil and traffic loads without structural failure.
Code of Practice for Laying of Concrete Pipes
Quick Reference Values
minimum trench width small pipesExternal diameter of pipe + 300 mm
maximum backfill layer thickness150 mm
minimum concrete cradle thickness under pipe1/4th of internal diameter or 100 mm, whichever is greater
minimum compacted cover over crown before heavy compaction300 mm
hydrostatic test pressure non pressure pipes2.5 m head of water
Practical Notes
Proper bedding (e.g., First Class, Concrete Cradle) is crucial; rigid concrete pipes can easily crack under uneven trench settlement or point loads if bedding is inadequate.
Trench width should be kept to the minimum necessary for working space, as wider trenches significantly increase the earth load (Marston's load) on the buried pipe.
Always ensure pipe joints (like collar or flush joints) are thoroughly cured and tested hydrostatically before backfilling the trench.