“Dusaro kaad nu pani” means water that has been re‑boiled a second time. In traditional Jain maryada, the “validity” of boiled water is counted in prahar (1 prahar = about 3 hours) and varies by season. Re‑boiling simply resets the clock from the time of that second boil.

Shwetambar practice (common maryada):

• Monsoon: up to 3 prahar ≈ 9 hours from the second boil.
• Winter: up to 4 prahar ≈ 12 hours from the second boil.
• Summer: up to 5 prahar ≈ 15 hours from the second boil.

After that time, do not use it; prepare fresh. Many also restrict drinking to daytime only. ( jainqq.org , jainworld.jainworld.com , jaininfoblog.wordpress.com )

Digambar practice:

• Generally, only freshly boiled, daytime water is used; it is not kept overnight. Specific hours can vary by acharya-sampradaya, but the emphasis is on using same‑day, freshly boiled water; re‑boiling, if allowed, is within the same daytime window. Follow your guru-parampara’s maryada. ( jainworld.jainworld.com )

Essence: Second-boil water lasts the same season-based prahar count as first boil, measured from the time of the second boil; when the limit ends, make fresh water. ( jainqq.org )