What size drain is required for a laundry sink or washing machine?

A laundry sink typically requires a one and one half inch or two inch drain line, while a washing machine standpipe usually requires a two inch drain to accommodate the high discharge rate. The drain must also include a properly sized P-trap and be vented to prevent airlocks or siphoning. We inspect your existing drain to determine whether it meets modern code requirements and whether it can handle the load from high-efficiency appliances. In older homes, we often find that the drain size is too small or the venting is inadequate. In those cases, we upgrade the entire system to ensure reliable drainage and avoid backups or overflows. Proper sizing and configuration of the drain is essential for long-term performance, especially in households with large or frequent laundry loads.