the sun evaporates the water and the water rises. clouds collect the water and when it becomes heavy, the water falls as rain. I don't know how the sun can drain water.
A few comets draw nearer to the Sun and accordingly lose mass all the more rapidly.
Long-period comets (those which take over 200 years to orbit around the Sun) start from the Oort Cloud. Danish space expert Jan Oort suggested that comets live in an immense cloud at the external scopes of the close planetary system, a long ways past the orbit of Pluto. This came to be called as the Oort Cloud.
The major constituents of a comet are ice, dust and water.
Comets don't generally have tails. They build up a fluffy, shell-like cloud known as a coma, and one, two, or three tails when close to the Sun.
