My understanding may be wrong, but I’m fairly sure I’ve seen water pumps moving up and down or back and forth. Wouldn’t that produce little bursts of water? How does it get so smooth and consistent?
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Many pumps do move water in pulses, but the pulses get smoothed out by a reservoir system between the pump and the stream. Homes have a pressure tank and towns have water towers. Even hand pumps can have a small reservoir that the piston fills. If the outflow nozzle is smaller than the piston, the reservoir fills and supplies the flow in the pumping gaps. It just needs a pump that can supply water faster than the flow rate.
Piston pumps are not commonly used for moving large amounts of water. Centrifugal pumps and lobed positive displacement pumps don’t have the same pressure related problems.
I would say several things here. First, many pumps are not piston-style displacement units that generate pulses of flow, but instead are continuous units like rotary pumps (many sump pumps are rotary units, for example, so no pulsing flow). You can and will see pulsing from a displacement pump (like a standard air-powered diaphragm pump used for emptying ponds at a construction site, for example), unless you get so far from the source that the flow is smoothed by pulse attenuation due to friction and pressure equalization.
The point is that pumps come in different “styles” (functional designs) and some do have an inherent pulsation to the operation, and some do not. Even when the pumping is pulsations, though, the flow will eventually smooth out, depending on how far from the source you go and what the system is like through which the flow is passing.
Not all pumps move up and down. This is a type called positive displacement pump. There’s another rope called dynamic pressure. [This](https://images.app.goo.gl/ZszLXh5cRcWdYEkEA) is a type of pump called a centrifugal pump. It works by flinging water outwards from the center of the pump to the outer edge using vanes. The water then flows out from an outlet on the outer portion of the pump.
These are actually more common and cheaper. Like you mentioned, they don’t pulse, but they also have fewer parts and are simpler.
And not all positive displacement pumps are up and down either. Some are based on screws or gears, not pistons. These are a lot smoother.
Edit: a lot of other piston pumps use a bunch of pistons, not just one ([like this](https://images.app.goo.gl/AoXKY8vfBLfVDFWE6)). this helps even things out.
Not all pumps “move up and down”. Those that do are designed to pump on both the up and down stroke. Many pump by turning a water wheel, some pump by turning a screw in a tube, some pump by spinning a turbine (a fan inside a tube), some pump by pinching a tube with rollers.
In the case of a piston pump pumping from a body of water like a lake or a well, there is a valve that prevents water from going back in your line and there is no air inside so the pump is not only pushing water but also pulling the water behind the pump. If you were to pump from a hand pump you would notice the different flow speeds but on electrical pumps, it is too fast to notice but there will always be variation in the flow.
I’m not positive… but I would say that once the pump has pulled the water up into the pipe it equalizes and creates a steady flow since the air was replaced with water. Saying that there’s gasket or diaphragm that’s continuously catching the water as you pump giving it a steady flow while the handles moving. Pausing the motion would cause the bursts. So the stream would flow as steadily as you pump it. Again not positive. It’s how I understand it to work though.
Since you say moving up and down,I assume you mean like a piston pump.
It could be a pump that “pumps” on both upstrokes and downstrokes.
It’s called a double displacement pump.
They’ve got a cool setup. You can see a picture [here.](https://i.ytimg.com/vi/lGF8eVhrD5c/hqdefault.jpg)
The general idea is that as you pull the piston up, you draw some water up from a pipe. When you push it down, you push that water out of the pump while simultaneously filling the upper part of the piston. When you pull the handle out, you push the water out of the top of the pump while drawing water in from the bottom. You can watch this in action at the end of [this video.](https://www.youtube.com/watch?v=2_p6WHZqeOQ) As long as you keep the pump handle constantly moving, you will always have a flow of water.
The majority of water pumps are centrifugal pumps which are essentially spinning water wheels
[https://2.bp.blogspot.com/-Gs8Ipwlnty0/WWYXXNqS2xI/AAAAAAAAIVA/s7k-P0qNjj4IIVeYxfu-smZBkMGWl4bNgCLcBGAs/s1600/centrifugal%2Bpump%2Bworking.png](https://2.bp.blogspot.com/-Gs8Ipwlnty0/WWYXXNqS2xI/AAAAAAAAIVA/s7k-P0qNjj4IIVeYxfu-smZBkMGWl4bNgCLcBGAs/s1600/centrifugal%2Bpump%2Bworking.png)
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