Slackline gear becomes dirty over time. That's no big deal, you can easily clean it in your washing machine or bath tub. This helps to keep your gear shiny and reduces wear over time. Here's how to do it:

* Put your webbing or rope into a pillow case or a net bag before putting it into the washing machine. This reduces tangling to nearly zero.
* There are detergents for synthetic fibres like sports clothes available in drugstores. These are very good for washing webbing and ropes, because your gear is made from the same fibres (polyamid/polyester). There are also special rope detergents available in outdoor stores. 
* Use low temperature programs like the hand wash program or the wool program. These are very careful to sensitive textiles, so they are best for your gear too. Max water temperature: 30°C. Please make sure that your washing machine can handle the load of your gear - clean it by hand in a bathtub if your machine can't handle the load.
* Most washing machines have an extra rinse program, it's worth using it after washing, to completely wash out all detergents. If you wash by hand, make sure to rinse well after washing too. 
* Don't spin dry or tumble dry your gear. For drying it's recommended to not hang the gear but to lay it loose on the ground in a shady place where the air can easily circulate. Turn it around after some hours multiple times, so that all parts can dry completely.
* You're done. Now take your gear, get out and rock some lines. Keep the balance :)