A spray bottle uses a pump to force fluid through a nozzle, similar to a car washer. When a user presses the trigger to release the fluid, the pump pulls the liquid from the bottle up a tube. The nozzle usually features a screw-on adjustment cap, and the piston retracts after each spray. The piston vacuum draws fluid from the bottle as it releases the fluid. A pump may fail if the nozzle is blocked, the seal around the piston is broken, or if the inner tube is not immersed in fluid.

One way to test the pump is to spray a liquid dye into the bottle. Then, place the bottle in a vacuum chamber. This will raise the pressure differential, which pushes the liquid through the pump. If the pump leaks the dye, it's likely the pump is faulty. You can tell if the pump is faulty by the dye leaking out of the bottle. A faulty pump will leak the dye, so you should inspect the pump regularly.

Spray bottles are typically used to dispensing chemical specialties, cosmetics, and cool cleaning agents. Before the 20th century, they had a rubber bulb that squeezed to remove the fluid, but these were quickly replaced by air pumps that forced the liquid out of a nozzle. The improvements in plastics since World War II also allowed for a greater range of fluids and made sprayers more affordable. There are many types of spray bottles available, including the one pictured above.

The principle behind pumping fluid from a bottle is very simple. Water has a low density, allowing it to move independently from air. It also has a low viscosity, which makes it flow easily. The pump head compresses the chamber space, and releases it again. This contact forces the liquid out of the bottle and creates pressure. This pumping action allows the fluid to move through the nozzle.

If you experience spray bottle problems, it may be because the nozzle is blocked or the piston seal is broken. In such cases, you may need to clean the nozzle by unscrewing it and trying to spray again. If the sprayer still does not pump the liquid, you may have to replace the sprayer, which may not be possible without access to the bottle. A few simple cleaning steps can usually solve the problem.