Answer

In many Jain traditions, water that was kept aside during a fast is thrown away after the fast because it is no longer considered fresh or suitable for use. It is usually discarded for cleanliness, purity, and to avoid consuming stale water.

Explanation

A fast in Jain Dharma is done with restraint and purity. The water kept during that time is often treated as part of the observance, not as ordinary drinking water. After the fast is completed:

• the water may have become stale,
• it may have absorbed impurities from being kept for a long time,
• and discarding it marks the end of the period of austerity.

In some homes, this also becomes a symbolic act:

• the fast is completed with purity,
• and one begins again with fresh, clean water.

Spiritual Understanding

In Jainism, fasting is not only about not eating. It is about detachment, discipline, and inner purity. Throwing away old water after the fast reflects:

• non-attachment to what was set aside,
• care for purity in daily life,
• and respect for the sacredness of tapas.

The main spirit is simplicity and cleanliness, not waste.

Takeaway

So, the water is thrown away mainly because it is considered old and unfit after the fast, and also as a symbol of purity and completion of the vow.