A few years back a so called "Mikvah-filter" was made by a few well meaning individuals. The filter would remain in the water filtering on a constant basis. No chlorine would be needed, the water will always be clean, etc.
What are the Halachic and "mesorah" ramifications of such a filter?
The creators of the filter made an appointment with the revered Rav Moshe Neuschloss, Z"L residing then and being the Rav in New Square, NY. When they appeared at the door of Rav Neuschloss for the appointment, Rav Neuschloss took his cane and "chased them out" of his home. Rav Neuschlos's son in law (Rav Shia Leifer) was there in the house at the time. When Rav Neuschloss was asked for an explanation by the one that arranged the appointment , Rav Neuschloss responded that he wanted them to respond to all that ask "what did Rav Neuschloss say about the filter?, He chased us out with a stick".
Rav Moshe Neuschlos's Z"L psak re: Mikvahs with these filters; was always ביום חול, לא להשתמש בכלל, בשוי"ט, אם יש כבר ילדים אז לדחות הטבילה ואם אין עוד ילדים לילך למקום אחר לשבת שיש בהסביבה מקוה בלי הפילטר.
Harav Moshe Shternbuch, Shlita-גאב"ד עדה חרדית ירושל-ם is also of the opinion not to use a Mikvah that has that type of filter. Rav Moshe Shternbuch, Shlita instructed his nephew (a Prominent Rav in Lakewood) to instruct his congregants and all others not to use such a mikvah and to re-toivel in a kosher mikvah. As far as we were able to determine, the nephew of Rav Shternbuch (A Rav in Lakewood) never notified his congregants or others of the psak of Rav Shternbuch.
Rav Sternbuch holds parts of it is a kli.
Everyone holds that the slightest modification will make it possul. The signing of the document not to modify does not help. Many have modified and passeled it R"L