Can one purify oneself from janabah by immersing oneself in a bathtub and then draining the water for prayer?

The sufficient act for a ritual bath (ghusl) after major impurity (janabah) is to ensure water covers the entire outer body, with the intention at the beginning of the ghusl. If you intended to perform the ghusl for janabah when you immersed yourself in the basin, and you ensured water covered your entire outer body, including reaching the roots of your hair, then your ghusl is sufficient and your prayer is valid, even if this is contrary to what is superior. The obligatory elements of ghusl are the intention at the first contact of the water with the first part of the body, and the covering of the entire body, including hair and skin, with water. Some scholars hold the view that if a person in a state of janabah immerses themselves in water less than two Qullas (160.5 liters), the state of janabah is not lifted, and the water becomes used (musta'mal).