Excavations at the Harappa site in Pakistan have revealed a series of concentric terracotta pipes equipped with tapered stone valves, identified as primitive water-pressure regulators. This sophisticated hydro-engineering system allowed the Indus Valley residents to manage the flow of water from large reservoirs into domestic drainage networks without overwhelming the clay pipes.
This find challenges current understanding of ancient plumbing, showcasing a level of hydraulic control previously thought to be exclusive to later Roman engineering. The presence of mineral deposits inside the regulators suggests they were in continuous use for over three centuries during the city's peak urban phase.