Locate the black holding tank outlet pipe on your vehicle or toilet. In most instances, the cap is located toward the bottom or underneath the frame. It may, however, be above the black water or sewer tank.
Remove the cap from the pipe if there is a separate valve that keeps waste contained in the black water holding tank. Skip this step if there is no cap. Check your manual for specific instructions on how to proceed.
Place the flexible pump tubing from the pump truck or pumping station on the opening of the black water outlet pipe. Secure it as directed in your manual or by the instructions on the pumping unit.
Open the valve on the black water holding tank to release the liquid and solid waste from your chemical toilet, if necessary.
Turn on the pump truck or pumping station and draw all the waste out of the chemical toilet.
Close the valve, if necessary, to seal the black water holding tank. See your manual for the exact procedure used on your particular vehicle or toilet model.
Remove the pump tubing from the black water tank outlet and replace the cap, if applicable.