The likelihood of you having to change your nixit in public is small as it will last for up to 12 hours.  If you are using a toilet without a sink, we recommend taking a small bottle of water in with you to rinse it, or wiping your nixit clean with some toilet paper and re-inserting.  A lot of our customers keep an extra nixit in their bag so that if they are caught out, they can replace their used nixit with a clean one. Either way, you can give it a more thorough wash later when you get home.