The maximum allowed distance from the finished floor to the center of the tee serving a clothes washer is ______________.

The maximum allowed distance from the finished floor to the center of the tee serving a clothes washer is 18 inches. This height ensures that the plumbing configuration allows for proper drainage and ventilation, which is vital to preventing issues such as backflow or clogs.

Placing the tee at 18 inches allows for the effective operation of the washing machine drain system, as it accommodates the typical height of washing machines and facilitates the gravitational flow of wastewater. Proper positioning is also important for maintaining clear access for maintenance and ensuring compliance with plumbing codes.

While the other options propose various heights, they do not meet the optimal standards needed for efficient plumbing design specific to washing machines. Hence, 18 inches is the correct measurement that adheres to the Omaha Plumbing Code requirements.