If a males elder sister is involved, the male has 3 days of asaucam; if it is a females elder sister, that female has 1 and ½ days of asaucam. That is if the elder sister attains Acharyan Tiruvadi at midday, asaucam is for that afternoon, night, and afternoon of the next day. On the next day, after sunset, asaucam is removed after taking a head bath. For such details please check the link below