It's not just copper coming from the hot water tap...it's other heavy metals, too, such as lead. As was said above, this is usually a problem in older homes (such as many homes here in NYC), but could occur elsewhere, too. I guess the only way to find out is by trial and error. My "killer" hot water did not test positive for copper either, but it killed the shrimp nevertheless. It's definitely not a "myth."
Because of the higher levels of heavy metals in some (used to be many) hot water supplies, hot water (from the tap) is usually not recommended for human consumption either.
Ultimate - removing chloramines and chelating heavy metals
Moderator: Mustafa