I owned a country property years ago and had a lot for trouble finding water and keeping the water drinkable (beavers kept flooding the well).

I ended up using a well on a unopened Municipal road allowance between the 2 lots I owned and it was a problem because I did not actually own the land the well was on.

When I went to the Bank to get a mortgage I had to prove both, that I had legal access to the well and that the water was drinkable. This involved an easesment from the local Municipality (they owned the Road Allowance), fixing the beaver problem and water testing by the local Health Unit. It was the same hassle when I sold the property as I had to prove to the buyer that the residence had a reliable, safe supply of water.

In your case if I was Property Owner A, I would politely tell the two other property owners that they needed to drill wells on their own land.

My .02 cents.

Mike