In general, it is not recommended to hook up a washing machine to the plumber's cleaning pipe (often known as a cleanout) that goes to the sink from outside. Plumber's cleanouts are designed for specific purposes, and using them for other functions, such as connecting a washing machine, can lead to various issues:
Capacity and Flow: Plumber's cleanouts are typically not designed to handle the large volumes of water and wastewater generated by a washing machine. Using it as a drainage point for a washing machine can lead to overflows or blockages due to inadequate capacity or restricted flow.
Backflow and Contamination: Cleanouts are usually intended for sewer access and maintenance. Connecting a washing machine to the cleanout can lead to backflow, where wastewater from the sewer line could potentially contaminate your washing machine or your home's plumbing system.
Local Building Codes: In many jurisdictions, there are building codes and regulations that specify how washing machines should be connected to the plumbing system. Connecting a washing machine to the wrong point in the plumbing system could be a violation of local codes and may result in legal or safety issues.
To connect a washing machine properly, it should be plumbed directly to a dedicated drainpipe or a laundry sink with proper drainage. If you want to install a new drainage point for the washing machine, it is best to consult a licensed plumber who can ensure that the installation complies with local building codes and is done safely and efficiently.
Always seek professional advice and assistance when making modifications to your plumbing system to avoid potential problems and ensure everything is up to code.