The toilet seal creates an airtight seal between the black tank and the inside of your RV, keeping the smelly odors out. Always make sure the seal is well lubricated and holding water in the base of your RV toilet bowl. Only use RV-safe cleaning products to avoid breaking down the toilet seal. Household-style toilet cleaning brushes with stiff bristles can also damage seals. If the seal appears to be dried out, use an RV toilet seal lubricant or plumber’s grease and apply according to product directions. A cracked toilet seal can be replaced easily and affordably. If you’d rather avoid DIY toilet projects, a certified RV technician can do it for you.