Rain Harvesting is an ancient and incredibly practical approach to supplying safe fresh water with relative convenience and affordability. Some research I've done on the subject suggests the area of Pennsylvania the prototype is being built in gets approximately 45 inches of rain per year (with it raining 155 days out of the year). This makes it quite suitable for a rain harvesting/catchment system. Assuming this is their only source for water, two people and a dog would need to harvest somewhere between 4-500 gallons of water per month. This includes all washing including clothes, drinking water, cooking and showers. This also assumes the toilet to be waterless and the shower to be "low-flow". Based on these parameters and using a calculation I found for converting inches of rain to gallons and based on the square footage of this model's roof (288 sq./ft.) suggests as much as 600 gallons of water per month could be harvested in this climate region, more than enough to support the inhabitants of the Ark.
