B's room has a sink right in the room, not separated by a door or anything. DH doesn't want to turn the water off because it's convenient to wash our hands there after a diaper change.
i said we either needed to buy the temp controller that mamaholmes suggested or turn off the hot water. Luckily DH finally agreed to turn off the hot water because this morning B dragged his stool over to wash his hands while we were in the other room. What a mess! But at least he didn't get scalded by hot water.