It looks like everyone has “run out of gas” as there have been no comments and no questions. I’m not sure how many people have gone through the sources or glanced at the teshuvot on line, so I will try to keep this short and basic.
In Leviticus Chapter 15, we see that at times both men and women can become “impure” and need to be “purified.” The male can be a zav (verses 1-15), meaning that he experiences some abnormal discharge from the penis. He can also be “impure” from a normal seminal emission (verses 16 -18).
The female as well is “impure” from her normal menstrual period (verses 19-24), when she is referred to as a nidda. She is also impure from abnormal vaginal discharges of blood (verses 25 – 30) when she is referred to as a zava (verses 25 – 30). All of these categories were in effect during Temple times, as impure people were prohibited from entering the sanctuary.
With the destruction of the Temple, the categories for the male no longer had relevance. The categories for the female would have dropped as well if it were not for additional verses in Leviticus (sources 4 and 5) which prohibited intercourse with a woman during the time of her impurity. Although it is not explicit in the Torah, the Rabbis learned (source 3) that a woman must immerse herself in water (a mikveh or natural body of water) in order to complete the purification process. Even if the flow of blood has ceased, she is impure as long as she had not undergone immersion.
According to the Torah, when a woman menstruates, she must count seven days from the beginning of the blood flow and that is it, as long as the blood has stopped. Then she can immerse in water. This practice of counting seven days apparently remained until the Tannaitc period (source 6), approximately the 2nd century of the common era.
At this point, the counting became different, as stringencies were added. The women would first have to wait until all bleeding ceased, and then they would have to add an additional seven clean days or “white” days to ensure that there was no extra bleeding. There is much dispute over how to understand source number 7. Some think that the daughters of Israel themselves established this more stringent custom where others believe it was the Rabbis who made this decree (source 9). The extra days apparently came about because of uncertainty whether the bleeding would render the woman a nidda or a zava (source 13). A zava would have to count seven days at the conclusion of her bleeding. Since there was confusion between a nidda and a zava, the Rabbis/daughters of Israel wanted to make sure that everyone counts the seven additional days, even the potential nidda.
Rabbi Susan Grossman believes that the enactment at Sadot was only for a far flung region where there were unlearned people. The daughters of Israel afterward accepted this more stringent custom. It is only a custom, and today observant Conservative women regret the acceptance of this minhag and would like to return to the previous situation of simply counting seven days in total from beginning to end.
Rabbi Avram Reisner arrives at the same conclusion out of different reasoning. Since women back then married young and were pregnant for much of their adult life, there was never time to establish a regular period or cycle of days. This led to the confusion of whether bleeding was at the appropriate time or not. Chances could not be taken with such a serious issue and every woman had to be treated as a zava gedolah, requiring the additional seven days after the cessation of blood. However, this is not the situation today. The vast majority of women have established periods for a few years before becoming pregnant and we know if the woman is a nidda or a zava.
I would add that an additional thought underlying these two teshuvot, at least that of Rabbi Grossman, is that today couples have busy urban schedules and are not home together every night at reasonable hours like in ancient times. It is overbearing to impose upon them celibacy for almost half the month, whereas in the rest of the month there is no guarantee that the couple will be together and not away on business, etc. Seven days are palatable and have a better chance of being followed.
Rabbi Miriam Berkowitz believes that we are not Karaites and there is no need to skip over the developments in the Talmud and return to a Toraitic practice. The seven extra days has become established practice (sources 11 & 12).
The common denominator among all three Conservative Rabbis is that the laws of family purity are still operative in our day and age.