Washing Machine Drain

I have lived in my house for 7+ years. Up until about 4 or 5 months ago, we weren't having any problems with our washing maching drain. When it drains, we can hear the water filling up the drain pipe. If we don't unplug the washer, the water overflows. What could be wrong now that wasn't wrong the first 6-1/2 years?

6 1/2 years of lint build up. call a plumber to snake the drain.

In addition to snaking the drain, you should check the size of the standpipe and drain line. In ye olden times, 1-1/2" was sufficient. However, today's machines pump their water out at a much higher rate so a 2" drain is not required. Even if your current machine is one of the older ones, eventually you will get a new one that will require the 2" so this might be a good time to upgrade if necessary. Have the plumber who snakes the clog examine your situation.