In Jain Dharma, boiled water (ukālelūṃ pāṇī) is used only for a limited time, called its “kāl” (time‑validity).

For a simple, general guideline for householders:

• Boiled & filtered water can be used up to about 24 hours from the time of boiling,

if it is: - boiled in daytime - properly filtered - kept covered in a clean vessel

• After 24 hours, it should be discarded and made fresh, because new tiny living beings (micro‑organisms) may develop, which goes against ahiṃsā.

During special periods (Paryushan, strict fasting, very hot weather), many follow stricter rules like using it within 3–12 hours only, depending on their sect and guru‑paramparā.

Exact hours can differ between Śvetāmbara and Digambara traditions and even between different saṅghs, so best is to follow whatever your own guru/saṅgh has prescribed.

You can read more here