The general rule is “don’t wash your rope unless you need to, but if you need to, don’t make excuses not to.”

When you need to do it is after your rope has been in contact with bodily fluids etc., and even more so if you are likely to use it on somebody else.

It’s a very good idea to keep a few ropes separate for that kind of use. Repeated washing at temperatures high enough to kill bacteria (50 degrees C at least) will weaken rope, so it makes sense to keep regularly washed ropes separate from, for instance, suspension drop lines.

Don’t use biological detergents. It’s very difficult to remove all trace of detergent from rope, and you don’t want those enzymes chomping away at your natural fibres when you think they’re all gone...

Use the minimum amount of non-bio detergent, and rinse several more times than usual.

To avoid rope tangling inside the washing machine ( or worse, escaping from the drum and tangling around the works), either chain-stitch it or put it in a mesh washing bag. Alternatively, hand-wash it!