I say, with Allah's guidance: Pumpkin water does not differ from pure water except in taste. If this characteristic becomes apparent, it becomes pure but not purifying for ritual impurity. It is permissible to remove actual impurity with it, but it is not permissible to perform ablution or ritual bathing with it. See: Al-Ikhtiyar, 1/20, Al-Lubab, 1/18-19, and Al-Hadiyah Al-Alaiyah, p. 39-40, and Allah knows best.