Rambam - 1 Chapter a Day

A mikveh is not disqualified, neither because of a change of its water's taste, nor a change of its smell, only because its color changes. Any substance that may not be used to constitute a mikveh initially disqualifies one, if it causes its color to change.

What is implied? Wine, milk, blood, or other liquids that are classified as fruit juices do not disqualify a mikveh if three lugim of them fall into it, because it was only said that three lugim of drawn water disqualify a mikveh. They do, however, disqualify it if they change the color of its water.

Even when a mikveh contains 100 se'ah and a log of wine or fruit juice falls into it and changes its color, it is unacceptable. Similarly, if a mikveh contains 20 se'ah or less of acceptable water and a se'ah of wine or fruit juice fell into it without changing its color, the water is acceptable as it was beforehand. The se'ah of wine or fruit juice, however, is not counted in the measure of the mikveh. If another 20 se'ah of acceptable water were added to the original 20, it is an acceptable mikveh.

There are substances that cause a mikveh to be considered acceptable and do not disqualify it; others that disqualify it and do not cause it to be considered acceptable, and others that neither cause it to be acceptable nor disqualify it.

These are the substances that cause a mikveh to be considered acceptable and do not disqualify it: snow, hail, sleet, ice, salt, and flowing mud. What is implied? When a mikveh contains 39 se'ah of water and a se'ah of one of these substances falls into it, the mikveh is acceptable and complete. Thus they cause a mikveh to be considered acceptable and do not disqualify it.

Even if one brought 40 se'ah of snow initially and placed them in a cavity and crushed it there, the mikveh is complete and acceptable.

These are the substances that disqualify a mikveh and never cause it to be considered acceptable: drawn water, whether pure or impure, water that was used for pickling, water that was used for cooking, a mixture of water and grape dregs before they become vinegar, and beer.

What is implied? When a mikveh contains 40 se'ah minus the weight of a dinar and the weight of a dinar of one of these liquids falls into it, it is not included in the measure of a mikveh and does not complete it. If three lugim of one of these liquids falls into a mikveh, it disqualifies it.

These are the substances that neither disqualify a mikveh, nor cause it to be considered acceptable: other liquids, fruit juice, fish brine, fish oil, and a mixture of water and grape dregs that became vinegar.

What is implied? If there was a mikveh that contained 39 se'ah and a se'ah of these liquids fell into it, it does not cause it to be acceptable. Nevertheless, the water the mikveh contains is acceptable as it was beforehand, for these liquids disqualify a mikveh only if they change its color, as explained.

There are times when the latter liquids cause a mikveh to be considered as acceptable. What is implied? A mikveh contained 40 se'ah, a se'ah of these liquids fell in, and then a se'ah was removed from the mikveh's waters. The 40 se'ah that remain still constitute an acceptable mikveh.

When one washed baskets used to collect olives or grapes in a mikveh, causing the water's color to change, it is acceptable.

Water of dyes disqualify a mikveh if three lugim fall in, but do not disqualify it because they changed its color.

When wine, black fluid from olives, or other fruit juices fall into a mikveh and change the color of its water, disqualifying it, how can it be rectified? If the mikveh contains less than 40 se'ah, one should wait until rain descends and changes its color back to water's natural color. If the mikveh contains 40 se'ah of acceptable water, one may fill buckets and pour water into it until its color reverts to water's natural color.

If wine, the black fluid from olives, or the like falls into a mikveh and changes the color of some of its water, if it does not have 40 se'ah of water whose color has not changed, one should not immerse in it. Even if it contains 40 se'ah, if one immerses in a place whose color has changed, his immersion is invalid. Even if a barrel of wine was broken and fell into the Mediterranean Sea and the color of the water in that place is the color of wine, one who immerses in that place is not considered to have immersed.

When even a dinar-sized portion of wine fell into three lugim of drawn water and change its color, so that they are all the color of wine and then they fell into a mikveh they do not disqualify it, unless they change its color.

When there are three lugim minus a dinar-sized portion of water and milk or fruit juice falls into the water, but its color remains that of water, it does not disqualify a mikveh if it falls into it. A mikveh is not disqualified unless three lugim of drawn water fall into it that were not mixed with any other liquid or with fruit juice.

When the color of a mikveh changes on its own accord without anything falling into it, it is acceptable. It is only disqualified if its color changed due to another liquid.