What happens when someone is using water when the water conditioner is running?

While the water conditioner is running, any other water being used in the house will be unsoftened.  The water conditioner will typically run the 3rd or 4th day of the week from 2 AM to 3:30 AM so it may not be an conflict.  A twin tank water conditioner will have soft water 24/7 because it has a backup tank.