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Excuse my terminology if it's wrong. I'd like to know if a venturi causes strain on a pump.

For example, in my drawing. I have an air pump behind the house with a 50mm pipe fitting. On the other side of the house is a pool with air jets with the same 50mm fitting. Best would be to just buy a lot of 50mm pipes and join the two around the house. Problem is that the 50mm is quite expensive. That made me think, would you just drop the side of the pipe in between and open it up again at the end and end up with the same result?

So to questions on this:

  • Would this cause strain on air pump because of it needing to "press the air into a smaller whole"?
  • Would your air output at the pool jets still feel the same?
  • Bonus question, would water work in the same way as air in this example?

Thanks for any help! This project made me very venturi-curious haha.

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  • $\begingroup$ A smaller pipe means the pump will operate at a higher pressure and move less air. Usually this should not damage the pump (but force the motor to run at lower rpm than designed for), to be sure we need a datasheet and the performance curve $\endgroup$
    – mart
    Jan 25, 2022 at 15:00

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A smaller pipe restricts the flow

Think of it like using a coffee stirrer straw to drink versus a big thick straw. Or instead of using a garden hose you used a thin piece of tubing. Or tried to move traffic using a 6-lane highway versus a single track dirt road.

The technical details behind it is that any fluid passing through a tube undergoes friction losses. A large diameter pipe has more volume versus the friction from the walls of the pipe (volume increases with the square of the diameter, circumference linearly with the diameter). Thus a thin pipe has more wall circumference versus volume. This is typically expressed as "head loss," and what you see in the pipe is that pressure goes down the further you go in a pipe. A thin pipe has more head loss.

Now, does it cause "Strain" on a pump? I doubt an air pump cares very much about the flow rate it passes. You can get into problems with a water pump if flow drops too much because the water provides lubrication and cooling. So really the only issue here is the reduced flow from the smaller pipe.

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