I am assuming, as most window cleaners have to declare that they carry a tank (as a modification) that you would have to tell your van insurance company that you have a dirty great big bin cleaning set up in the back of it. They will class it as a modification and charge you more. If you have an accident, and you havent declared that you have the bin cleaning set up, then they could get out of paying you.
Im with A Plan and they know about my jetwash/tank set up in the van.