Use of a Tammi 4 without immersing it
Question
Is it permissible to use a cold water machine without immersing it?
Answer
Two things need to be clarified:
Whether the water comes into contact with metal or only with plastic. We do not have information regarding a specific company, but in many containers, the water is in a metal container.
Secondly, whether the item is entirely manufactured abroad and not assembled in Israel, and whether a technician is required for installation, as an ordinary person does not know how to perform professional installation. If it was assembled in Israel or if the technician needed to install the machine itself [not just external pipe connections], the vessel does not require immersion. Additionally, if, when replacing the filters, inserting the new filters and returning the machine to operation requires the knowledge of a technician, and an ordinary person cannot perform this action, then, after filter replacement, the vessel does not require immersion.
Source
Shulchan Aruch (Yoreh De'ah 120) Chochmat Adam (Ch. 73, §13).