We decided to try out the Karcher HDS 7/104M on a trailer which has many years of accumulated dirt on it, using Karcher's RM806 High Pressure Cleaner and a Foam Lance. Karcher recommend diluting the RM 806 at ratio of 1:3. We used it at 2%, which is the maximum suggested. This machine delivers 700 litres/hour at 100 bar. Our estimate for the cost of the chemical used was approximately 60p for this demonstration. We also used a Foam Lance to apply the chemical which helps it to adhere to the side of the trailer, giving it more time to work.