Washing Machine Drains into Sink (How to Fix It!)

Is your washing machine water backing up into a nearby sink? Learn why this happens and how to correct the drainage issue.

The Backup Problem

It's a messy surprise: you run a load of laundry, and dirty, soapy water backs up into the adjacent utility or kitchen sink. This occurs because the washing machine and the sink share a drain line.

Why It Happens

• Partial Clog: A partial blockage downstream from where the two drains meet forces the high-volume water from the washing machine to seek the path of least resistance—up into the sink.
• Undersized Drain Pipe: Older homes may have 1.5-inch drain pipes, which struggle to handle the rapid water discharge of modern washing machines.

Fixing the Issue

The first step is snaking the shared drain line to remove any lint, soap scum, or debris. If the pipes are undersized, a plumber may need to upgrade the drain line to a 2-inch pipe to handle the volume.