If you wish to explore this route, there will have to be an agreement concerning who will pay for the filtration mechanism, how much will it cost to maintain the system, and whether any adjustment is appropriate to the purchase price. All of these scenarios are ultimately property specific. Make sure that the proposed treatment mechanism is legal in your community. Make sure that experts believe it will work. Make sure that sources of off site contamination have been stabilized so that the problem will not worsen or change.
Some States have funds set up to assist home owners with bad well water.
In such cases, the buyer and seller need to determine who will apply for such funds, and who will benefit from the proceeds if they are forthcoming. Again, competent legal and engineering counsel is required to evaluate these kinds of options. In conclusion, even dream houses require drinkable water. Bad water can make people sick. Before purchasing a house, qualified experts must evaluate the quality of the potable water supply, and provide viable alternatives in the event the water is inferior.