During Paryushan, the simple, traditional rule is:

• Drink only boiled and filtered water in daylight.
• Start after Navkarsi (about 48 minutes after sunrise).
• Stop at sunset (no water at night until the next day after Navkarsi).

By vow/type:

• Upvas (fast): only boiled/filtered water from Navkarsi to sunset; none after sunset. Some do Nirjala (no water at all).
• Ekasana/Ayambil: water only in the same window (Navkarsi to sunset), and take minimal sips.
• Tivihar/Chovihar: no water after sunset. In Tivihar some also stop water after noon.
• Samayik/Pratikraman: avoid drinking during the ritual unless truly necessary.

Tradition notes:

• Shwetambar Paryushan (8 days) and Digambar Das Lakshan (10 days) both generally follow the above daylight rule; some Digambar practitioners keep stricter limits (e.g., stopping water after noon on certain vows).

Practical points:

• Use freshly boiled water (same day) and strain it (rajoharan/cloth).
• Avoid ice, flavored drinks, or unboiled water.
• Health exceptions are allowed; protecting life (including one’s own) is foremost in Jain Dharma.