How do I go about ensuring the concentration of Auto-Foam is correct for my pressure washer?

Fill up the detergent bottle or reservoir with exactly one litre of water. Take a large bucket or container and discharge the lance into this until the detergent bottle is empty. Measure the total amount of water collected, and multiply this number by 0.04. This is how much Auto-Foam you need to use in your detergent bottle or reservoir for the correct concentration. When you have measured the Auto-Foam into the bottle or reservoir, make this up to one litre with water. This method will create the correct concentration of Auto-Foam discharging from the lance, as this depends on the rate at which the reservoir is emptied during use.