Originally Posted By: marantz
I would also beware of any temporary arrangement, as continued long enough, B and C might find a lawyer that would claim your friend had granted them a permanent water claim or easement.


Marantz makes an excellent point ... "implied easement by prior use" and "easement by necessity" might be claimed, legitimate or not ... once people gain even a temporary foothold, they're often reluctant to relinquish without a fight.
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"Things that have never happened before happen all the time." — Scott Sagan, The Limits of Safety