There are several reasons why the coffee output does not match the freshwater input.
- The dry coffee grounds absorb twice their weight in water (which stays in the coffee grounds and does not make its way into the carafe).
- There is water loss due to steam and residual water left in the coffee maker (that does not make its way into the carafe).
A cup marking on our carafes is approximately 4.75 oz. To get 4.75 oz of coffee it takes approximately 5.25 ounces of freshwater. About 0.5 ounce of freshwater is lost per cup of coffee. A 12 cup batch loses approximately 6 ounces of water or about 1.25 cups.
Add an additional 1.25 cups of freshwater to get 12 cups of coffee output. Of that 1.25 cups of lost freshwater - about 5.4 ounces (1.13 cups) remains in the wet coffee grounds and 0.6 ounces (0.12 cups) are lost to steam and residual water remaining in the system.
This is normal operation for all brands of coffee makers.