As the title states, what are the conditions that need to be met for the Quality Well in Old Tristram (Act 1) to become available? For those who do not know what I'm referring to, there is a well that looks like a standard sprite in Old Tristram and sometimes this sprite will fill up with water and you can battle the zombie QA team from Diablo 3. I have yet to see the well filled with water and accessible, so I was wondering if I needed to meet some hidden prerequisites or if it's a truly random Easter Egg.
Here is a video of another player accessing and exploring the well for reference.
Best Answer
The only condition or requirement is that you must have completed the game on normal difficulty and be playing on at least nightmare, other than that, it is simply chance. If you keep reloading the area(by exiting and reentering the game), you should eventually come across it.
Please note that given the lack of information on these Easter Egg dungeons, the requirements above may not be entirely accurate, but thus far I have yet to see this dungeon, in game or on the internet, before nightmare difficulty.