Draining a washing machine is not quite the same as draining a sink. Unlike a sink, a washing machine has a pump that ejects water under what is called positive pressure. If something stops the water from getting to the sewer, for example, it may have enough momentum to back up into a nearby drain, such as that for the dishwasher.
The cure for backed up laundry room sinks and washing machines is a call to All Drains Plumbing. Joe Canty of All Drains serves the area around Bensalem and Bucks Counties including parts of the Philadelphia area. You might be surprised to learn all that they do. Just visit alldrainsbensalem.com and discover more, then call Joe at the number nearest you.