In Jainism, during fasting (upvas or other vrata), it is customary to drink only boiled water to minimize harm to microorganisms. According to Jain tradition, once water is boiled, it should ideally be consumed within 24 hours (prahar) during daylight hours only. Some stricter sects, such as the Sthanakvasi or Terapanthi, further refine this period and recommend consuming boiled water within 6 hours or 12 hours, especially in hot weather, to ensure minimal new life forms develop in the water.

Always follow the guidance of your Jain tradition or guru, but the general practice is not to consume boiled water after 24 hours from boiling.