I've been using a backpack sprayer for applying wet&forget, canvas waterproofing, plant liquid food, etc. It has been great if one doesn't mind carrying a 4 gallon backpack, constant pumping to maintain pressure and topping up contents for the 4 gallon tank fairly often. I needed something that doesn't require topping up content ever so often and unused content can be returned to original container! Hence, decided on this self-mixing hose-end sprayer. Both hose-end sprayer and backpack sprayer have its pros and cons. It all depends on your needs.