When a boat is equipped with wastewater reservoirs, distinction is made between “grey” water from <br>the kitchens and bathrooms and “black” water from toilets. These reservoirs can cause bad smells and blocking when waste matter becomes silted up. Nowadays, biological formulas are most commonly used in eliminating waste and greasy substances. Based on non-pathogenic bacteria and <br>enzymes, they guarantee the total liquefaction of waste matter. Conventional chemical products are reserved as additional disinfecting agents where required. Bio products, in order to be effective, must be used in exactly the right doses, at the right intervals, and for the right length of <br>time. Never mix conventional chemical products with bio products in the same tank, as this can render the bio product useless.