You can, however, pour a small amount of water into a bowl and then pour a larger amount of holy water into a bowl and then it will all be considered holy water.
This is what I have heard as well. By the same logic, you could take your pint of holy water from the OP, add half a pint of normal water, and you have 1.5 pints holy water. You can then add another pint of normal water, and you have 2.5 pints holy water. Add two more pints of normal water, and you have 4.5 pints holy water. Finally, you can add the last 1.5 pints of normal water to obtain 6 pints of holy water.
Using a similar approach, but on a continuous basis, you could slowly (maybe 1 pt/min) pour your 5 pints of normal water into a large bowl containing your 1 pint of holy water. After half a minute, you’ve added half a pint normal water to the holy water to total 1.5 pts holy water as the remaining 4.5 pints normal water continues to flow in. You can grasp the rest. One way to dispute this approach would be to insist that you have to wait until the pouring is done to count your quantity and determine whether the normal water becomes holy water. However, if that is true, then at the 30-second mark your large bowl has dilute 67% holy water, only later to become all holy water or all normal water.
Obviously if you can do it with a slow pour, you should also be able to do the same with a fast pour. As long as there is no split-second when the quantity of normal water coming in contact with the holy water is greater than the total quantity of holy water, you should be able to pour your 5 pints normal water into the 1 pint of holy water, and have the whole thing become holy water in the 2-3 seconds it takes to pour.
On the other hand, pouring a pint of holy water into a bowl of 5 pints normal water will immediately eradicate the holy water. In fact, using my logic from the last paragraph, pouring 5 pints of holy water into 1 pint of normal water will continuously convert the holy water to normal water as the small amount of holy water being poured each second comes into contact with the larger pint-plus of normal water.
Finally, things become a bit less clear when it’s uncertain which is being poured, or how far the mixing zone of the “pour” extends. Say you have two connected pint bags - one of normal water, one of holy water, floating in space. The barrier between them is broken to allow mixing. At first a milliliter of normal water comes into contact with 2 milliliters of holy water, resulting in 3 ml of holy water. Then that blob of water comes into contact with half a teaspoon of normal water, resulting in just over a teaspoon of holy water. Next comes half a tablespoon of normal water, and the resulting blob becomes all normal water. But when it bumps into a tablespoon of holy water, suddenly the whole thing is holy water again. Back and forth it goes until either the holy water or the normal water gets the better of this process, and the entire 2 pints become either holy water or normal water - but there is no way to tell in advance which it will be.
This makes it hard for me to explain how it is not a magic trick, as
Mrs Sally says.
If that can happen then I’m so going to do that! 