The idea of having keilim that are difficult and sometimes impossible to tovel is not a new phenomenon. The Chochmas Adam (73:13) discusses very large vats that were used for beer and explains that they do require tevila. He dispels the notion of being attached to the ground and no longer a keli. He elaborates in the Binas Adam (66) about the concept of כל המחובר לקרקע כקרקע and why it doesn't apply here - since it was turned into a keli prior to being fixed into the ground. Since it is not possible to tovel them, he suggests making a very large hole rendering them unfit and having a Jew fix it. At the end he then retracts since the beer that is stored in them is unfiltered and is not fit to drink, and with this justifies the custom of not being tovel these vats. But in the Binas Adam he is reluctant to rely on this heter because it should be no better than a shechita knife which is still fit to use for other foods that are eatable.
Regarding equipment that is plugged into the wall, some want to be matir without tevila based on the concept of being attached to the ground and losing the status of a keli. The chochmas adam would seem to reject this idea even if it were actually fixed to the ground. But perhaps one can argue that a keli that is functional prior to being attached to the ground, will not lose its status of a keli by being attached. Yet, an electrical keli that is not at all functional until it is plugged in, will have a status of a keli that is קבעו ולבסוף חקקו and therefore not require tevila. Obviously, this sevara is a difficult one because the keli doesn't need to be attached to the ground to work, it only needs to be attached to electricity which is often attached to the ground, but can technically be attached to a battery as well - therefore even when attached to the ground may not lose it's status of being a keli.
I am a big proponent of toveling electrical appliances. I have done so many times and so long as they are properly dried before plugging in, don't present any problem at all. However, last year someone gave me a Keurig Coffee maker as a gift. This coffee maker is not just a plug in appliance but actually has an electronic circuit board and display screen. Toveling it would be tantamount to toveling a laptop - even a drop of remaining water on the inner board can short circuit the entire machine (and then even costco wouldn't take it back). It isn't clear that a keli that would be ruined by tevila is exempt from tevila. It is very possible that such a keli cannot be used. A friend of mine showed me a pesak from R. Dovid Feinstein in 1973 where he wrote that for something that would get ruined one can rely on a sevara that it contributes very minimally to the food such as a toaster which just browns the bread - see l'torah v'hora'ah here. But, this sevara wouldn't apply to our situation.
At first I thought that it should be permitted since the entire machine is plastic which doesn't require tevila. But, I called the company and found out that the element inside the machine which heats the water is certainly metallic. Does this machine require tevila?
I have what seems to be a good justification to exempt this machine from tevila. As I said, the entire machine is plastic, so the only part that is metallic and would be mechayev the entire machine tevila is the inner metal tubes which the water travels through to heat it up. The halacha of tevilas keilim is that "beis hastorim" - hidden areas of the keli, don't require tevila (y.d. 202:5, and last taz). Unlike tevila of a person where there is a problem of chatzitza even on beis hastorim because they need to be fit for bi'as mayim, the halacha by a keli is that it doesn't need to be fit for water to touch and can have a chatzitza. It is for this reason that we don't require one to immerse a keli until all the air bubbles empty from the inner parts of the keli - because the areas that aren't visible don't need to come into contact with the water. This coffee maker is constructed in a way where we have no parallel in the keilim of chazal. The food actually comes into contact with the beis has'tarim of the keli, and that is the only metallic part of the keli (aside from the pin that opens the pod like a can opener). Therefore, even if one were to be tovel this coffee maker, the metal tubes inside wouldn't have to come into contact with the water because it is just beis hastorim. It seems completely illogical to say that the part of the keli which is mechayev the entire keli in tevila wouldn't even need to come into contact with the water, yet the keli would require tevila. At least when we require tevila to a keli where the ma'amid is metal (even though the metal doesn't come into contact with the food), the metal nails and screws would come into contact with the water. But in our case where the metal part of the keli is beis hastorim and wouldn't need to come into contact with the water, it doesn't seem logical to say that the metal inside would still be mechayev the plastic part of the keli to be toveled (of course a keli that has metal and requires tevila, must be fully immersed so that even the plastic is toveled, but here the only part which would be mechayev tevila on the keli doesn't need to be immersed and therefore wouldn't be mechayev the keli to be immersed). After consulting R. Nota Greenblatt and sharing this sevara, he concurred.
FOR A VERY GOOD SHIUR ON THIS ISSUE FROM MY BROTHER - SEE HERE.