If you don’t want to mess with the plumbing or it’s hard to access, build a slightly raised drain pan for the washing machine. Then just run a PVC pipe from the drain pan through the wall on a slight downslope to end 4-6″ out from the house. Or don’t raise the drain pan and run the drain down through the garage to the ground.
This is an emergency drain, not one that will be used on a normal basis, so flooding your yard or promoting mould is a non-issue.
If you’re concerned about un-conditioned air getting in, put some sort of rubber flap on the end of the pipe that won’t open unless water needs to come out.
If you wanted to go 100% ghetto, you could just open a hole in the floor, cover it with a grate, and have any leakage leak into the garage. Most garages are built on a slope to allow any water on cars to drain out via gravity.
