It actually wasn't poisonous given the circumstances.
Could you elaborate? Just because it was less poisonous than it could have been, does not make it non-poisonous.
I dunno I read it somewhere that some other thing in the pipes formed a protective layer that prevented the lead from actually seeping into the water or something
Same thing happened in Flint Michigan, the lead pipes weren't the issue; They stopped treating the water a certain way and the slight acidity in the water caused (iirc) some sort of calcium carbonate or sodium bicarbonate layer to be washed away until the acidic water started leaching lead into the water.