How should the waste from a clothes washing machine discharge into the drainage system?

The waste from a clothes washing machine should discharge indirectly into the drainage system using an air break. This method is critical because it prevents wastewater from potentially backing up into the washing machine, which can lead to contamination. The air break creates a physical separation between the discharge outlet of the washing machine and the drainage system, allowing air to enter and reducing the risk of siphoning and backflow.

Using an air break also complies with plumbing codes that require systems to be designed in a way that protects potable water supplies from possible contamination. This setup is particularly important in ensuring that foul water from the washing machine does not return to the clean supply, maintaining health and safety standards in the plumbing system.

Other methods, like using a standpipe or a sump pump, while they can be used in certain situations, may not provide the same level of protection against contamination as the air break does. Direct discharge can pose significant risks, as it lacks the necessary protection measures to prevent backflow incidents.