2,140. A Mistaken Practice

Hilchos Issurei Biah 11:13

Similar to the previous halacha, if a woman had a wound that was bleeding, or if blood came out while she was urinating, she remains ritually clean. Additional practices were only instituted regarding women who see ritually-unclean blood as we have explained, plus that all different shades of blood are treated as ritually-unclean.

Hilchos Issurei Biah 11:14

In some places, the practice is for a woman to act as a niddah for seven days even if she only saw blood on one day. After this, she counts seven clean days. This practice is not correct. Rather, it’s a mistake on the part of whoever ruled this way and it’s not deserving of consideration. If a woman has one day on which she sees blood, the proper course of action is to count seven clean days and immerse on the night of the eighth day – which is the second day after her niddah days – after which she is permitted to her husband.