Mikvaos 1:1

There are six degrees of mikvah, each better than the next. If a ritually-unclean person drank from a pool of water and then a ritually-clean person drank from it, he is rendered unclean. If an unclean person drank from it and then drew water from it in a ritually-clean utensil, the utensil is rendered unclean. If an unclean person drank from it and then a loaf of trumah fell into it, if a ritually-clean person rinsed the loaf in the pool water, it is rendered unclean; if he didn’t rinse the loaf in it, it remains clean.

Mikvaos 1:2

If someone drew water from the pool using a ritually-unclean utensil and then a ritually-clean person drank from the pool, he is rendered unclean. If someone drew water using an unclean utensil and then drew water from using a ritually-clean utensil, it is rendered unclean. If one drew water using an unclean utensil and then a loaf of trumah fell into the pool, if he rinsed the loaf in the pool water, it is rendered unclean; if he didn’t rinse the loaf in it, it remains clean.