Plumbing engineering in Indian subcontinent even 5000 years ago was quite sophisticated and accorded high priority. The Indus Valley Civilization sites in the Indian subcontinent evidence of public water supply and sanitation systems built with ingenious and advanced engineering.
The recently discovered Rakhigarh excavations revealed world's first urban sanitation systems where individual homes or groups of homes were supplied water from a well. From a room set aside for bathing, waste water flowed to covered drains over major streets.
A typical example is in Lothal in Gujarat, where all houses had own private toilets connected to a covered sewer network built of brickwork using gypsum based mortar. The urban areas of this civilization included public and private baths. Underground sewer drains connected to wider public drains were built with precisely laid bricks and a sophisticated water management system was in place. Some of these sophisticated systems included drainage channels, rainwater harvesting and huge reservoirs/baths, covered sewers etc.
Such emphasis on sanitation continued across centuries through the eras of the Mauryas, Guptas or the Vijayanagara empire. Sanitation has always been integral to India's cultural foundation.