Does a hot water urn need to be toveled? If so how is it done that
I am assuming that you are asking about a simple hot water urn, and not one that has digital display and a computer chip. A hot water urn needs tevila, even though it plugs into the wall, this will not render it mecubar l’karka and it still needs tevilah. However the urns that have water pipes attaching them to the wall would not need tevilah.
The whole urn, should be placed into the mikvah, however it should not be immersed mikva face down, because air will get trapped inside it and the water will not reach the whole cavity of the urn. Therefore put in into the mikva at an angle so that the cavity can fill up, and then turn it right side to remove any air pockets.
Then, the urn should be emptied of all its water, try to get out any water that got into the electrical parts of the urn, and let it dry out in the sun or a different hot place for 2 days, (a blow dryer will speed up the process) . After the water has evaporated and the wires are dry, the urn will be safe to use.
Regarding the cord of the urn, it is controversial and many poskim say that it doesn’t have to be toveled. It would be preferable however to tovel also. If the plug detaches from the urn three is no need to tovel it.
Avoda Zara 75a (see Igros Moshe Y:D 3-24 and Y:D 1-57), Ohr Yitzchok 2- Y:D 17-3, Ohel Yackov Tvilas Keilim pg 257, 259, R’ Y. Berkowitz shlit”a. Hilchos Tevilas Keilim 66, The Kosher Kitchen chap. 18 ftnt. 30, Habayis BkashrusoTvilas Keilim 1-ftnt 37, Kovetz Mbais Halevi 15 pg. 81 ftnt 10.