Question :

Is it a condition that a woman should untie her locks while making Ghusl(ritual bath) ?

The Answer :

Ghusl from Janabah(ritual impurity), or menstruation obligates that water reaches the roots of the hair in order for the Ghusl to be valid, but if it doesn`t, then hair locks must be untied for water to reach them, and for Ghusl to become valid.