I will use a common pressure washer to clean straps and, rarely, winch line, but I won't launder winch line. I have done it, but I probably took a year of service out of the line by doing it. The UV coatings are not all that durable to start with, and detergent will take them out of the rope, accelerating their break down in sun light. Mine went from blue to white in one washing in a net bag and wash machine, and looked fuzzy afterward. Not a good sign.
Laundering doesn't get all the dirt out of rope anyway, so a good rinse in a tub of warm water is as good as anything, in my opinion. High pressure water tends to fray 12-strand braid rope, so I go easy on the pressure if I use the wand. A good garden hose at standard house pressure is sufficient.