Originally Posted by Fat AJC
abilities and moves that redirect a attack do not have the redirect function working if the attack strikes more than one mon.
they still give their immunity/absorb function if they do so.
Water spout is a all enemy targeted attack as such it ignores the redirect effect of storm drain.
Correct, but to also add, the SpAtk boost for the Pokemon with Storm Drain ability still triggers, and gets it's boost. All other Pokemon will be damaged normally.