Some Common Uses for High-Pressure Pumps
The need to transfer water began with the first humans who cupped their hands to collect it from streams. However, it was a further million years or so before the first recorded use of a mechanical device for transferring water. The so-called “shadoof” was the first step towards the development of the modern high-pressure pump. It consisted of a bucket suspended by a rope from a pivoted pole and balanced by a counterweight.
Next came the screw pump invented by Archimedes. Centrifugal and plunger models followed between the 15th and 17th centuries. Today, there are numerous devices based on these early inventions. Although still used to convey water, chemical solutions, oil, air, gases and even thick slurries are also pumped for various purposes.
The high-pressure pump is a more recent development and has many practical applications. Technically, a pump is a device whose purpose is to create a flow of liquid. The faster the device operates, the greater the volume of fluid conveyed in a given time, known as the flow rate. When reducing the size of a pump’s outlet, the flow rate will also become reduced, and this causes the pressure of the ejected liquid to increase. 
This is the same effect that occurs when adjusting the nozzle on a garden hose. It also hints at one of the earliest uses for a high-pressure pump, namely cleaning. A garden hose is helpful for simple cleaning tasks like rinsing mud from a driveway but its output would be useless for clearing the scale from the interior of a forge. The first pumped device for cleaning purposes appeared during the late 1940s. It consisted of a handheld lance with an adjustable discharge pressure of between 400 and 500 psi, higher than the hose but still well below that of comparable devices in use today.
The high–pressure pump has since found applications in more challenging cleaning tasks, often in automated systems. The automatic carwash has become a common feature of filling stations worldwide, allowing the driver to remain in the car as the machine successively washes, rinses, and air dries it. The same principle of using water jets to clean vehicles extends to the automated wash bays where encrusted earth-moving equipment is blasted at considerably higher pressures to ensure it is fit for reuse.
If you happen to occupy the penthouse of a high-rise apartment block, before water can reach your taps, it must overcome gravity. While ground-level pressure might be around 80 psi, this would probably not help anyone living beyond the third floor. Overcoming this limitation could require installing a high-pressure pump on every third or fourth floor.