Moved into a 2 story townhouse recently and bought a new over/under washer and drier. While doing some wash my wife noticed that when the washer drained it backed up into the sink. The lucky thing was it was a small load.
This morning was an extra large load, and it backed up so bad that it filled the sink (but did not over flow) and continued to back up until it came out of the washer drain.

My initial thought is there is a clog in the drain somewhere and I need a snake or auger to clean it out.

But I remember the installers taking out the air gap for the dishwasher, could this also be related ( I have had no issues with it backing up).

Both the dish washer and washer/drier are in the kitchen.

Need some help, please.

TIA

Go with your first impression. Removing the air gap has nothing to do with your back up. Get out that trusty snake because you have a partian blockage in the washer/sink drain line. A partial clog will let you drain your sink but your washer pump discharges with great pressure and increased volume and can't completely get past the clog so it backs up into the sink. Your clog is located downstream from the sink so you will have to snake from the kitchen sink roof vent, unless the builder left a clean out in the vertical stack. More questions? I'm as close as a click. Good luck, Tom

Thanks for the information. ;D
I'm unsure if there is a clean out in the vertical stack, the house was built in 1965 and we have found a few things that we know aren't up to today's codes.
What is the sink roof vent you speak of, is that actually the vent on the roof?
Could I run the snake from the sink trap instead?

The vent you will have to snake is located directly above the kitchen sink if your sink is on a outside wall. You can not snake through the trap. You will run into a tee. From the roof you will have a direct shot at it. Drop your snake down the vent until it hits the bend at the bottom of the stack and then run it out out about 15 or 20 feet to be sure you're in the main. Hope this helps, Tom