Short answer: Yes.

In the Shvetambar tradition, Attham tap is three continuous upvas (fast-days) without doing parna in between:

• Day 1: Tivihar upvas (no food; only boiled water allowed during daytime).
• Day 2: Tivihar upvas (same as above).
• Day 3: Chauvihar upvas (no food and no water for the full 24 hours; nirjala).

Parna is then done on the 4th morning within the proper time, beginning with boiled water, according to local maryada. Take proper pachchhakkhan (vow) at the start and renew it each sunrise.

Digambar practice recognizes a 3‑day anshan (tridivas anshan). Rules about taking water vary by local deshachar; many observe it as full anshan (no food), with or without water as per vow.

Please follow your guru’s guidance and your sangh’s maryada, and only attempt this if your health allows.