lol, I had the same question not long ago! My adopted brit mum (from a Brit friend in the US) insists that the way to combat the gray in hardwater country is to soak the whites in a tub with a little bit of bleach BEFORE doing the actual load in the machine. Therefore, one avoids putting the bleach directly into the machine.
I imagine that this might be particularly wise as hardwater country machines take a BEATING from the water enough as it is. Longer running cycles and more chemicals in the machine might not help its longevity.
If you're a renter--this is less of a concern, of course. But if you own the machine, it is probably worth at least a year, if not three, more on the life cycle of the beast. Maybe.