How to Remove an RV Holding Tank

Close both valves on your tank and remove the tank's sewer cap.

Place the hose adapter over the outlet. Turn the adapter clockwise until you feel it locking into place.
Attach the other end of the hose to the park's sewer connection by using the other hose adapter.

Open the tank's valve (at the end of the hose attached to the sewer line) to let the water flow out. The large valve releases the black (toilet) water tank, and the small valve releases the grey (dirty tap water) tank. Make sure to release the water from the correct tank, or release the water from both tanks if you plan on removing both. Detach the hose from both the sewage end and the tank end.

Turn off your water pump, and ensure your RV is not connected to the city water supply. Unscrew the water connection behind the toilet by turning the connection counter-clockwise.

The way toilets are attached to the floor varies. Many are attached by nuts and bolts. You'll probably be using a socket wrench to detach the toilet from the floor, but use whatever method is appropriate for your toilet. Lift the toilet out.

Unscrew the floor flange from the tank's top using the socket wrench. Support the tank's weight with the floor jack.

Remove the tank from the tank straps. You should be able to do this by loosening the straps with your hand, or unhooking them, depending on your tank type. Cut the tank line (which runs through the top of the tank) with a pocketknife.

Lower the floor jack, allowing the tank to hit the ground. Go outside, and drag the tank out from underneath the RV.