Bottom top all in one portable toilet fluid cleaner size 2 litres bottom top was listed as an essential product by practical caravan for 2013 and is now our number one selling product so as you would do with any blue or green chemical pour a shot into your waste tank and then as you would with any rinse pour into your top tank bottom top has a pleasant subtle smell of lavender to neutralise any unpleasant smells in the bottom tank it will break down waste and in the rinse tank as yo