Something else your friend might want to check with the local municipality they are in. It may not be legal to share water with out at least meeting water quality guidelines. Which would require periodic testing, filing the test reports with the state or local government. And even if it is not it might be a good excuse for your friend to use. "I called the county and they said that a plumbing permit would be required and it cost $$$, there will also be monthly testing which cost $$$, and they said that the fine for not following local laws would be $$$$ per day. And I didn't tell the county that you are sharing water now, I wouldn't want you to get in trouble with the law." If your friend's neighbors are to lazy to keep their property maintained they will be to lazy to call and check the law for themselves. Or just tell them NO and leave it at that.