Dometic DTK976 additional tank for Dometic 976 toilets. If you want to be out and about in remote places, you should store a spare tank on board. It may never be needed - but it gives you a sense of security. The compact Dometic DTK976 replacement tank for the Dometic 976 portable toilet takes up little space. So you are optimally prepared. A replacement tank in case you need one. Only for emergencies. Can be easily stored. 18.9 litre capacity.