When you use your washing machine, your machine fills with water at various points in the washing cycle. Once the machine completes the cycle, it must drain the water quickly. A properly functioning washer is able to do this without problem even though it discharges a large amount of water in a short amount of time. Problems occur when the machine is not able to discharge this water quickly enough.
Washing Machines and Kitchen Sinks
Your washing machine and kitchen sink all connect to the same plumbing system that both provides the water they need and allows it to drain away. Both your kitchen sink and your washing machine discharge into the wastewater line as all the other appliances in your home, though the two may be closer to one another or drain into the same main line. A problem in this line can impact both the washer and the sink.
When your washing machine causes your sink to back up, this is normally a sign of a problem in your home's water drainage system. The drain is likely clogged or otherwise blocked and preventing the washing machine water from draining quickly enough. Because the water has to go somewhere, it backs up into the kitchen sink drain because that pipe leads to the same gray water drain line as the washing machine. Fixing the clogged drain typically requires you to run a pipe snake line to push the blockage through. You may need to contact an experienced plumber to do this.
In some situations, your pipes may not be caused by a clog at all. In older homes, the drain pipes themselves may be the problem. If you've purchased an older home that has never had a washing machine, for example, the drain pipes may be too small to accommodate the washer discharge. In this situation you'll have to contact a plumber to discuss what options you have in addressing the inadequate drainage system.