A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills.
Penstocks for hydroelectric installations are normally equipped with a gate system and a surge tank. Flow is regulated by turbine operation and is nil when turbines are not in service. Maintenance requirements may include hot water wash, manual cleaning, antifoulant coatings, and desiccation.
Penstocks are also used in mine tailings dam construction, the penstock is usually situated fairly close to the center of the tailings dam and built up using penstock rings, these penstock rings control the water level letting the slimes settle out of the water, this water is then piped back under the tailings dam back to the plant via a penstock pipeline.