New to water heater

[Stan@FourWheel]

Fresh water tank only holds 20 gallons.

When empty, there could be 1.5 - 2 gallons of water in the tank still below the drain hose port.

Hot water heater holds 6 gallons (separate from the fresh water tank).

 

[Wallowa]

Fresh water tank only holds 20 gallons.

When empty, there could be 1.5 - 2 gallons of water in the tank still below the drain hose port.

Hot water heater holds 6 gallons (separate from the fresh water tank).

Stan...was told you can't drain the last 1 gallon out of the hot water tank...true?