Ruling when tahur water cannot be told from pure non-purifying water
When tahur water cannot be told from pure but non-purifying water, how is one to purify himself?
One weighs the signs and acts on the stronger likelihood, performing wudu from the vessel he judges to be the tahur one; if the two are equal, he performs wudu from both.
One performs wudu as many times as there are pure vessels plus one more — here, from each of the two vessels — and prays a single prayer.
One weighs the signs between the tahur water and the pure non-purifying water, such as used water, and purifies himself with the one he judges to be tahur, without performing wudu from each; but with water and rose-water, he performs wudu once with each and does not weigh the signs, on the soundest view.
One performs a single wudu from both, taking for each limb a handful from this vessel and a handful from that, covering the whole limb with each handful, and prays a single prayer.