Why do we place Kalash in puja rituals

The Kalash is a sacred symbol in Hinduism. It is a copper vessel that has a large and round base with a narrow mouth at the top. It is also known by other names such as Purna Kalasha, Purna Kumbha, and Purna Ghata. According to the Rig Veda, the Kalash is not a mere vessel kept during puja or ritualistic ceremonies; it represents abundance and the source of life.
During religious ceremonies or pujas, devotees fill the kalash with holy water and place a coconut on the mouth of the kalash, with the pointed end of the coconut facing upwards towards the sky. Sometimes, betel vines and mango leaves are also placed around the mouth of the kalash and at times, it is also filled with coins, gems and gold as an offering to the almighty.

Kalash represents abundance and wisdom. Hindu Gods and Goddesses, including Lord Brahma, Lord Shiva, and Goddess Lakshmi, hold a Kalash in their hands, which symbolises creation, purity and prosperity.
As per popular belief, Kalash is the personification of Lord Ganesha, who is the remover of obstacles from our lives, and Gauri Devi, goddess of household bounty. Devotees worship Kalash, an image of Devi, during Hindu festivals associated with childbirth and marriage. We can place Kalash near the entrance of our houses as a sign of welcome, facing the North, in the center. The North implies balance, and by placing Kalash in that direction, we are inviting balance and happiness into our lives.

Many devotees believe that the metal pot represents fertility.It stands for the Earth and the womb, which are the nourishers and providers of life. The mango leaves depict the Kama, the god of love. Through its usage, we are invoking the pleasure aspect of fertility. Coconut presents prosperity and power. The water in the Kalash symbolizes the life-giving principle of the universe.

As per tradition, the structure of Kalash is as such, it represents the five elements, known as Pancha Bhoota
The metal pot represents Prithvi (Earth).
The water inside symbolizes Apas (Water)
The neck of the pot relates to Agni (Fire).
The opening stands for Vayu (Air).
The coconut and mango leaves at the top represent Akasha (Ether)

The water from the Kalash is used for kumbha Abhisheka or is sometimes poured on a Tulsi plant. This water is spiritually charged, and it attracts positive vibrations. Apart from that, it plays an important role in the purification process during rituals.