Thought someone may be interested. Seems some Dometic toilets are leaking water from the bowl into the holding tank. The culprit is the "Ball Seal". Replacement is easy.
Happy trails,
------------
Dometic® 300/310/320 Flush Ball Seal Installation
NO TOOLS REQUIRED.
1. Turn off water supply.
2. Hold flush pedal down to keep flush ball open.
3. Grasp inside edge of seal and pull upward to remove from toilet.
4. Thoroughly clean lower bowl rim area where seal was located.
5. Release flush pedal to close flush ball. Thoroughly clean surface of
flush ball.
6. Insert new seal in base, making sure seal is firmly pressed outward
against lower bowl rim.
7. Press flush pedal to open flush ball, and spread thin layer of silicone
grease or petroleum jelly under the seal where it will contact flush
ball. Release flush pedal.
8. Lightly press down around circumference of seal to insure seal is in proper position.
9. Turn on water supply.
10. Add water to bowl and check for leaks.
--------------------
For a photo click here:
http://bryantrv.com/docs2/docs/dometic310ballseal.pdf