Knapsack sprayer is a 16 litres container with a manual hand pump and spraying mechanism. it is suitable for garden watering, fumigation of homes and industrial uses. Durable and general purpose spraying. A sprayer is a tool that will spray liquid materials such as fertilizers, pesticides, herbicides or even water. A sprayer used in this way will need to be able to calibrate for those materials (fertilizers, pesticides and herbicides) that are being applied.