What is the maximum number of side-by-side clothes washers on a 4-inch horizontal waste line?

The maximum number of side-by-side clothes washers that can be connected to a 4-inch horizontal waste line is determined by the capacity of the waste line to handle the discharge flow from the appliances without causing backups or drainage issues.

In this case, the Omaha Plumbing Code specifies that a 4-inch waste line can adequately accommodate the drainage needs of up to 22 standard clothes washers when they are placed side-by-side. This is based on appropriate calculations of drainage fixture units (DFUs) assigned to each washer, and the combined flow must not exceed the line's capacity to prevent clogs or inefficient drainage.

The specific figure of 22 reflects established standards within plumbing codes, ensuring safe and efficient operation of the plumbing system without exceeding what the waste line can handle.