Answer

In a Tivihar Upvas, you may drink boiled water during the permitted daytime period, according to the rules you have taken.

Generally, if your household/guru’s practice allows water after Navkarshi, then you may drink boiled water at Navkarshi. You do not necessarily have to wait until Porsi unless that is the specific rule or vow you have accepted.

Explanation

In Jain practice:

• Chauvihar Upvas means no food and no water.
• Tivihar Upvas means no food, but boiled water is allowed during the proper time.

The timing for drinking water can vary by tradition, family practice, or guidance from one’s guru:

• Some follow drinking water after Navkarshi.
• Some stricter practices may wait until Porsi.

So the correct practice depends on the niyam you have taken.

Takeaway

If your Tivihar Upvas niyam is simply “boiled water allowed,” then drinking boiled water after Navkarshi is generally acceptable. But if you specifically vowed to start water only after Porsi, then you should wait until Porsi.