Napisan as toilet treatment in Public Forum Posted March 19, 2018 · Report reply From Jacky Jacky in 2012 You may find this of interest. This is from the Thetford Australia website in Maintenance Tips section: "Maintenance tips for your toilet The waste tank seal, the automatic pressure release vent seal and the cap seal must be cleaned regularly. When the toilet is being used frequently, monthly cleaning is generally sufficient. We advise cleaning the seals and valve blade with Thetford Bathroom Cleaner. Note! Never use household cleaners (Solvents or other powerful cleaning agents). These may cause permanent damage to the seals and other toilet components. For cleaning your toilet: Squirt Thetford Bathroom Cleaner into the toilet bowl. Flush the bowl with water and wipe down the rest of the toilet with a damp cloth. Tip! For a really shining toilet, dry it with a soft dry cloth after cleaning. Thoroughly clean the seals and valve blade, using Thetford Seal Lubricant and wipe them over with a cloth or a piece of toilet paper. Repeat the above operation if the seal and blade are dirty or if opening and closing the blade is difficult. Note! Never use Vaseline or any vegetable oil. These may cause leakage. When the toilet is not being used for a long period, it is advisable to clean the seals and then coat them lightly with Thetford Seal Lubricant. This will ensure that they remain in good condition (supple). N.B. The valve blade seal is a part of the toilet that is subject to wear. Depending on the extent and manner of maintenance, after a certain period the seal will lose quality and must be replaced. Back to top." We use Olive oil to lubricate the rubber around the blade seal and have done so without any problems. Giving the cassette a good soak, as suggested in previous posts, empty and let dry out also helps reduce any odour and 'plaque' build up.