Sorry, not Chełm. And the reason to bottle that water from the spring has a more practical nature - it excludes drinking, at least not in such amounts as you can see in the photos.
Looking at the plaque... maybe this is a Licheń type place? That is did some kind of special religous event take place there and so people collect and/or sell the water?
Clever answer but no. Although it might sound quite plausible - collect holy water for the whole year. :):):)
Hint - this spring with special water is located in a spa resort town or city. Alien mentioned Ustroń but it wasn`t. It is an unusual spa resort which most people visit for different reasons than health problems.