If you’ve ever used a soap dispenser, you know how to operate a pump. You press the top down and soap comes out. When you first use the dispenser, though, you have to push the top down a few times before the soap comes out. This is because the pump is initially full of air, and needs to be filled with the soap before it can be dispensed. You also learn quickly that sprayers and pumps don’t work if you turn them upside down. If your container is clear, you can see a tube running from the pump down to the bottom of the container. If the container is upside down, then the tube can’t get any liquid in it. So keep your sprayer or pump upright for best results. If you are satisfied with these two pieces of information, then feel free to skip the next section. However, if you want to learn about how exactly a pump works, read on.