Immersion must be in a pool or spring (or river or ocean; see 201:2,5) that contains a volume of water equal to at least 5760 eggs (“40 seahs”; see 201:1). In a spring the water may be either still or flowing (continuously; see 201:13), but if the water is primarily rainwater or melted snow it must be still; see 201:2. On cases involving both flowing and still water see 201:10-12,14,50-51. In any case the water must be from natural sources; it must not be “drawn” by hand or in a utensil (201:3). Any amount of drawn water may be added to a spring of any size or to a pool that contains at least 40 seahs of water (see 201:15,40), but if a significant amount of drawn water (“3 logs”: the volume of 18 eggs) is added to a smaller pool the entire pool is regarded as “drawn” (see 201:15-22). (On the definition of “drawn” water see also 201:34-49. On the degree of interconnection required to combine two bodies of water see 201:52-60, as well as 62-64. On doubtful situations see 201:4,65, 67-74.) The water must be on the ground (201:5, and see 57); it may be in a structure attached to the ground, but not in a utensil (see 201:6-8, 66); but utensils may be immersed inside other utensils (see 201:9;202:6). Immersion must be in water, not in other liquids, and not in a pool of water in which other liquids have been mixed so that its color changes; such water is also not invalidated by being “drawn” (see 201:23-29). “Drawing” does not invalidate ice or mud, and if drawn water freezes it is no longer regarded as drawn (201:30-31; see also 32-33). Immersion in a natural hot spring is permitted, but opinions differ on adding warm water to a pool and on bathing after immersion (201:75).
Immersion of a person or utensil (see Ch.10a) requires complete covering by water all at the same time (198:1). Dirt, articles of clothing, or any other object which interferes with contact with the water invalidates the immersion if (a) most people would object to its presence, (b) the person immersing him- or herself personally objects to its presence, or (c) if the object covers the majority of the surface of the person or utensil (198:1,202:2); for examples see 120:13;198:2-29,41-47;202:1-5. The custom regarding women’s immersions, however, is that even insignificant amounts of foreign matter, as well as loose objects – such as loose articles of clothing – not be present (198:1). Certain types of knots in a person’s hair may also interfere with contact with the water and invalidate the immersion if any of the three conditions above are met (see 198:5).
Contact with an object under the water is not interference since the surfaces that are in contact are already wet (120:2;198:28,30, and see 33). An immersed person must be in a relaxed posture so that parts of the body that are usually visible are not pressed together so as to interfere with contact with the water (198:35-39; see 201:61,66). Body cavities that are not usually visible do not require contact with the water, but there should be nothing adhering to them even internally; see 198:43. Cavities or handles of utensils do require contact with the water; see 120:22 and 202:6-9. An immersed person must not be supported under the water by any object that is susceptible to impurity (198:31-32). If possible a woman’s immersion should be supervised to ensure that it was complete (198:40), but it should not be public knowledge (see 198:48) and should not take place where there is a chance of being seen by outsiders (198:34).
To ensure that there are no obstacles to total immersion a person’s body and hair should first be bathed in warm water, combed, and examined closely (199:1-2). This should preferably be done just before immersion, but if this is impractical (for example, because of holidays) it may be done in advance and care taken to ensure that the body and hair remain free of obstacles (199:3-8). If it was not done the immersion is invalid even if nothing was found on the body or hair afterwards; see 199:8-9. If it was done and something was found on the body afterwards, see 199:10-13.
The person immersing a utensil first recites the blessing “…Who commanded us about immersion”. It is customary for a person who is being immersed to recite the blessing after the immersion but before coming out of the water (120:3;200:1).
Shulchan Aruch, Copyright (c) 2000 ProjectGenesis, Inc.