I would also agree with Perikles. If yours is only about a meter deep, which is very shallow. I think it would be a mistake to seal it.
10 months in the life of a well built possel is nothing. According to the previous owners of our house, our's is almost 60 years old and still working no probs. But like Perikles ours is very deep.
But one note of caution if you are flushing paper it will clog the possel up and it will over flow. I am afraid that the 'bins' in the toilet is a way of life here.
