Follow-up
Actually, it is 3/4" in a very large house with 4.5 bathrooms, 2 jacuzzi tubs, 4 showers, a bar, 2 kitchen sinks, 2 dishwashers, and two large 75 gallon water heaters. It is emblematic of some of the dumb short cuts the builder took with the house. :(
Fortunately, there are only...