We noticed that the standpipe that the washing machine drains into was overflowing whenever we did a big load of laundry. There was the pricey -- and just plain painful -- option: Tear open the wall, rip out the old iron pipe, plumb in a larger pipe, and connect it to the sewer line under the house.
And then there was the realistic option: Install a fatter and taller standpipe and hope that that provides enough extra room for the water to hang out in while it drains.
It took several trips back to the hardware store to find the right type of connector between the p-trap and the threaded iron nipple sticking out of the wall. (Hint: don't worry abou the threads, just get a neoprene gasket.) But it works! Not bad for $25.