A long, long time ago I worked for a company that had an old
Hydramaster with a split shaft PTO. The dump valve for the waste tank was right next to and slightly behind the driver's seat on the left side. You could easily reach it while driving and more than once was dumped while driving down a dirt road. The actual drain was in-line with the tires, so if someone was following you, they couldn't see the waste water flowing out. They would however get a mess on the front of their car. It was especially nice to do that to tailgaters.