Short answer

• If you are fasting with water (sājala upvās), drink only boiled, filtered water during daylight.
• Stop before sunset. Best practice: stop one antarmuhūrta (about 48 minutes) before sunset.
• After sunset: no water.
• If doing nirjala upvās: no water at all.
• Start in the morning only after sunrise; many follow the stricter rule to wait about 48 minutes after sunrise.

Notes by tradition

• Shwetāmbara: Commonly allow boiled water only from after sunrise until before sunset; many end at least 48 minutes before sunset.
• Digambara: Often stricter; many observe nirjala (no water). Where water is allowed, it is still daytime-only and boiled.

Helpful details

• Use freshly boiled water; many follow within-the-day or shorter “validity” (some 3–12 hours in stricter practice) to minimize himsā.
• Always follow the pachkhan (vow) you take and your sangh/guru’s guidance.

Related guidance

• Tivihar/Upvās water timing
• Last water during Paryushan (sunset rule)
• Boiled water “validity” while fasting
• Pachkhan for “water-only” upvās