One summer's day I got a phone call from a father of a large fun-loving family. He, along with his family, had packed into their van and were on their merry way to France for a vacation. While en route, they were hungry and started to check their inventory for what to consume. They had packed lots of sliced bread and a large stick of salami, but they had forgotten to pack a knife. For the moment, they were managing by passing the salami around, and each child took a bite. They then realized that they could buy a knife from a souvenir shop, but it would require tevilah, immersion of vessels before it could be used. The halachic question quickly arose: How could they go about toveling (“immersing”) the knife as they were crossing the English Channel?

Hang in for the answer.

Metal and glass utensils that were bought from a non-Jew are to be immersed in a kosher mikvah prior to use for food.

1) The sea is a valid mikvah, and new utensils may be dipped therein. Natural lakes are also valid mikvaot. Rivers have a different rule: their validity as a mikvah depends on whether their water is sourced from springs or from rains.

The water in most larger rivers is primarily sourced from springs, although the rivers may swell noticeably in the rain season. But my concern is more about mountain rivers, that flow only in the warmer weather, and are fed from the melting snow at the mountains' peaks. Melted snow has the same status as rainwater, that it is valid as a mikvah only when static, but not when flowing. So, you cannot immerse vessels in a mountain river.

2) I must add here what I heard from Rabbi Y.Y. Feigelstock of Buenos Aires:

Most large rivers today have been harnessed for producing electricity. This involves diverting most of their waters through turbines. The turbine is by definition a “‘keli”, a ‘vessel’, and consequently, all waters gushing out of the turbine are invalid for tevilah, as if they had been drawn by a bucket (“mayim she’uvin”). These invalid waters can be made kosher again through hashakah, when they will come into contact with kosher water. But hashakah is only effective when the waters are standing, not if they are flowing.

So, before relying on a river for tevilah, you need to verify that it has no electricity-dam somewhere upstream.

3) When no kosher mikvah is available, there is a short-term solution: to give the utensil to a non-Jew as a gift, and then borrow it back. Utensils that were borrowed from a non-Jew do not require tevilah.

4) For the same reason, if you wish to have a cold drink in a glass that belongs to a non-Jew, you don't need to worry about tevilat keilim.