Question: Is it Halachically acceptable to cover the base of an electric appliance with clingfilm or something similar, and immerse it in a mikva in this fashion, or does this constitute a chatzitzo?
Answer: This idea is acceptable (albeit not ideal) – provided that the plastic used to cover the base section is only covering a minority of the utensil and that the plastic will remain in place for at least seven days.
This is because there are different categories of chatzitzos: A chatzitzo that covers a majority of the utensil is problematic and will invalidate the tevila even if one is not makpid about the presence of the chatzitzo. But regarding a chatzitzo that covers a minority of the utensil, if one is makpid about the chatzitzo it is problematic and will invalidate the tevila mid’rabonon, but if one is not makpid about the chatzitzo and it only covers a minority of the utensil, the tevila is valid.
Returning to our scenario, if the plastic cover is only covering a minority of the utensil and it will remain in place for at least seven days, we can consider the plastic a mi’ut she’eino makpid and it is acceptable to immerse the utensil in this fashion (c.f. Chelkas Ya’akov Volume 2 Siman 61 #6 who presents a similar suggestion).