Hi Rabbi. I am studying the laws of mikvaot and I was wondering what is the classification of a standard pool or jacuzzi? Is it considered a mayan or a mikve? Theoretically if it would be a mayan, then the 40 seah requirement would not apply, correct? For example, in South Florida the water comes from the Biscayne Aquifer which is like an underground river. Then the municipality pumps it from a well and then it gets treated and distributed. Is a well pump considered sheuvin? By allowing pools are we relying on the opinion that says that sheuvin that travels on the ground more than 3 tefachim is valid water for a mikve even if it makes up all 40 seahs? Why does the filtration process in a pool not considered flowing and thus invalidating the mikve? Also, what is the main reason why most rabbis would say that a pool would not be a kosher mikve? Is it because of the rain water? In reality, the Biscayne Aquifer gets its water from rain that percolates through the Everglades down into the Aquifer. So does that mean that it still is rain water when it comes out of our faucet? Thank you in advance for your clarification.
Hilchot Mikvaot is one of the most complicated areas in Halacha. It is not a simple sugya that appears neatly in one place. The laws are spread throughout Mishnayot, Gemara, Rishonim, and later Poskim, and many rabbis unfortunately learn only short summaries or repeat accepted assumptions without fully understanding the underlying sources. That is why people often receive very strange or contradictory answers on these topics.
First, I would recommend dropping the entire “mayan” issue from this discussion. A mayan means an actual spring. If you want to classify something as a mayan, then you would need to immerse in the spring itself. Once the water has been pumped away, processed, distributed through municipal systems, and gathered into a pool or jacuzzi, we are no longer discussing immersion in a natural spring.
In any event, the distinction is not especially relevant for your question. Even according to the opinions regarding a mayan, you still need enough water to immerse the body properly. The practical discussions of mayan are often more relevant to kelim, where one can immerse small objects in a natural spring even without forty seah gathered in one place.
So for practical purposes, treat a swimming pool or jacuzzi as a mikveh issue, not a mayan issue.
Your next question was whether the filtration system or circulation makes the water “flowing water” and therefore invalid. The answer is no. This is a misunderstanding of what “zochalin” means in Hilchot Mikvaot. Running water refers to a river or stream continuously flowing in its natural course. A pool with pumps circulating water internally is not considered a flowing river. If a person stood there with a bucket repeatedly scooping and pouring the same water back into the pool, nobody would call that a river. Mechanical circulation inside a contained body of water does not create the halachic category of zochalin.
The main issue people usually raise is mayim she’uvim — drawn water. Here again there is tremendous confusion. Many people mistakenly think a mikveh must specifically contain rainwater. That is not what the Torah says. The issue is not “rainwater” versus “tap water.” The issue is whether the water became drawn in a portable vessel — a keli.
Modern plumbing systems are attached to the ground (mechubar l’karka). Underground pipes, municipal water systems, fixed plumbing, and permanently connected hoses are not portable kelim. The water travels through infrastructure attached to the earth. That is fundamentally different from somebody drawing water in buckets or containers and pouring them into a mikveh.
Therefore, if you have a swimming pool containing forty seah of water, and the water entered through standard municipal plumbing attached to the ground, we consider the water valid and not classify it as problematic mayim she’uvim.
People often quote the Noda BiYehuda on this topic, but most of those quoting him never looked carefully inside. If they did, they would see that his concerns are not addressing standard modern plumbing systems attached permanently to the ground in the way people assume.
As for the Biscayne Aquifer, yes, ultimately its water originates from rainwater that percolated naturally into the ground and accumulated underground. But again, the real issue is not whether the source was originally rain. The halachic discussion revolves around whether the water became invalidated through being drawn in a keli. Water moving naturally underground or through systems attached to the ground is not transformed into mayim she’uvim simply because it later emerges from a faucet.
This is why many of the common assumptions people repeat regarding pools and mikvaot are based more on inherited slogans than on careful learning of the actual sugya.