What is the maximum number of back to back clothes washers allowed on a 4 inch horizontal drain?

The maximum number of back-to-back clothes washers that can be connected to a 4-inch horizontal drain is 30. This specification is derived from plumbing codes that ensure adequate drainage capacity, preventing issues such as overflow or clogging.

Clothes washers generate significant water volume and require proper drainage to function efficiently. When multiple washers are connected to a single drain line, it is crucial to consider the drain's capacity and the potential for simultaneous discharge. A 4-inch horizontal drain is designed to handle a specific flow rate; exceeding this limit could lead to drainage failures.

The calculated limit of 30 allows for enough water to be adequately discharged while maintaining the system’s integrity. This standard helps ensure a practical balance between efficiency and prevention of plumbing issues, adhering to the overall plumbing code requirements that aim to promote safe and effective drainage systems.