Parah 5:9-6:1

Parah 5:9

If one put two stones next to one another and made a trough from them – and the same is true of two kneading troughs and of a trough split into two –  the water in between them is not sanctified. If they were connected with lime or plaster so that they can be moved as one, then the water in between them is sanctified.

Parah 6:1

If a person was preparing the sanctification water and the ashes fell on his hand or on the side of the trough and from there into the trough, it is invalid. If the ashes fell from the tube into the trough, it is invalid (because the ashes are supposed to be thrown into the water by hand). If he took the ashes from the tube and then sealed it, or if he closed a door, the ashes remain fit but the water is rendered unfit (because the water is invalidated by performing some other task while involved with the purification). If he put the tube upright on the ground, the water is rendered unfit. If he holds the tube upright in his hand, the water is fit because there’s nothing else he can do.