Thetford manufacturers a commonly used line of RV toilets. The gasket provides a watertight seal between the toilet and the flange. If the gasket fails to do its job, a leak will result from underneath the toilet. Fixing the leak is a job that an RV owner can accomplish alone. Be certain to fix this problem as soon as you notice it to prevent any possible water damage.
Shut off the water pump that is on board the RV. Or shut off the valve that connects the RV to the city water supply. Press the toilet's flush lever by hand, or step on the foot pedal, to flush the toilet. Keep the lever or pedal pressed down to drain all the water out of the bowl.
Unscrew the water supply line from the water valve/elbow on the rear of the toilet. Twist the screw counterclockwise, using an adjustable wrench, and disconnect the line from the toilet.
Remove any shroud from the base of the toilet, such as on the Bravura model. Remove the two O-rings, and remove the shroud from the STYLE Plus model. Remove the bolt caps that are installed over the two closet bolts in the toilet base. Using a wrench, remove the nuts from each of the closet bolts.
Lay newspaper on the floor nearby. Lift the toilet straight up, off the flange and flange bolts. Invert the toilet on top of the newspaper. Wipe with a rag what is remaining of the old gasket off the bottom of the toilet. Press the replacement gasket in place around the discharge outlet on the toilet bottom, with the gasket's lip side down.
Remove the rag from the flange and with the rag wipe the flange clean of any residue from the old gasket. Position the toilet above the flange, aligning the holes in the toilet base with the flange bolts. Lower the toilet onto the flange. Press down on the toilet with your body weight.
Install the nuts on the flange bolts. Hand-tighten each nut, and use the adjustable wrench to alternately tighten each nut until the nuts are snug. Do not overtighten. Install the bolt caps. Install any shroud onto the toilet.
Connect the water line to the rear of the toilet, tightening the connection with a wrench. Turn on the RV's water supply. Flush the toilet and check for any leaks from underneath or behind the toilet, at the water line connection.