blocked sink unit?

I take it its a space saver sink unit ie: wash in it and wash up in it. I might be grease if its the type described. Caustic soda and water just off the boil.
Then buy a wire drain cleaner from DIY store or plumbing shop give it a twirl down the pipe if you can't get it to go down sink because the sink drain had side outlet then work from outside up as far as it will go. Wear rubber gloves.
If you haven't tried already DON'T do what (I) says as if that does work you'll be cleaning out the bathroom the mess it would make.

Bob
June 2011

the outlet pipe on a camper van cant be that long,, i would go outside and find the outlet pipe for that sink, were it comes out of the wall, get a garden hose, put it up the outlet as far as it can go, and turn the water on, to flush it out, or you can keep poureing( boiling) water down the sink till it unblockes it,

l
June 2011