Papavinashanam

Papavinashanam (The Cleanser of sins).

About 5 Kms north of the Tirumala temple is a deep bowl formed by the surrounding hills that created a reservoir ages ago and many a mountain stream emptied into it. This came to be known as the Papavinashanam (The Cleanser of sins). Its waters were initially used for worshipping purposes but abandoned later because of the distance from the temple. It is still used though,for special occasions. To conserve water forever increasing number of pilgrims and therefore, the temple township, a dam was constructed across but the pilgrims, thus preserving the tradition, provided a bypass for bathing. It is believed that the holy waters of this place dissolve the sins of the devotees. Hence this place is known as Papavinashanam. A dam constructed here regulates the water flow. 

Source : http://www.tirumala-tirupati.com