Nikhil Ramkarran says:

Physics is your friend. This, at its most basic, is a foot valve at the end of a hose. How it works:1. The foot valve prevents liquid in the hose from flowing out that end.2. Each time you push the end with the valve down into liquid, more liquid enters the hose but cannot flow back out.3. When enough liquid has entered the hose and the top of the liquid in the hose is below the valve (the end in the liquid) gravity takes over and your liquid will flow into the an empty container which is at a lower level than the full container.The proper technique then is not to “shake” the end in the liquid but to push it down into the liquid so that each time it goes into the liquid, more enters the hose.The foot valve does not form a perfect seal when you pull the end out of the liquid, so a little will flow back out. The key then is to push it down and pull it out fairly rapidly.Used correctly, this is a brilliant product which I have used frequently over the past 2 years and which my mechanic had previously recommended to me. And it is even cheaper now than when I bought it. The instructions suck though.