All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The water that was changed due to staying long without being used remains pure; it is pure in itself and it is a purifier. Ibn Taymiyyah said: 'The water that changes because of staying still and unused remains as it is in principle, (i.e. it is pure) according to the agreement of the scholars.'
Allaah Knows best.