The Elsan Tank Fresh doesn't just mask smells from your sinks, showers and drains it eliminates them completely from your grey water system. Great for motorhome and caravan waste tanks. Used regularily, Tank Fresh also dissolves grease build-up to help keep everything clean, fresh and free flowing. Once you've tried it, you'll never put up with bad odours from your grey water system again. Add 20ml of Elsan Tank Fresh for every 10 litres of grey water tank capacity. Adding a little through each drain will also improve standards inside the pipe-work.