How do I calculate / convert GPM to PSI ?

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Discussion Overview

The discussion revolves around calculating the necessary pump specifications for creating a current in a 30-gallon live bait tank for tuna fishing. Participants explore the relationship between flow rate (GPM) and pressure (PSI), as well as the impact of pipe size and hole dimensions on water flow dynamics.

Discussion Character

  • Homework-related
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant describes the scenario of needing a water pump to create a current in a bait tank, estimating a required speed of around 2 MPH.
  • Another participant converts the speed to meters per second and suggests that if the hose size is reasonable, a swirling flow can be achieved at that speed.
  • There is a repeated emphasis on the importance of the size of the holes drilled in the pipe, with participants questioning how this affects the flow.
  • A participant references a water flow chart to provide additional context on how pipe length, diameter, and resistance influence flow rates.
  • Calculations based on fire department flow charts are mentioned, indicating how different hose sizes and lengths can affect GPM and PSI, although these examples may not directly apply to the current scenario.

Areas of Agreement / Disagreement

Participants express uncertainty about the specific calculations needed and how various factors like pipe size and hole dimensions will influence the required pump specifications. There is no consensus on the exact formulas or values needed for the calculations.

Contextual Notes

Limitations include potential missing assumptions about the tank design and the specific dynamics of water flow in the described setup. The discussion does not resolve the mathematical relationships between GPM and PSI for the given scenario.

kck
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Ok I should say up front I am not near as brilliant as you fine folks, I was a C student now I am a Dad that can't figure his 11 year olds homework out . I hope someone will be so kind as to help me lol.

Scenario:
We are going tuna fishing, so we need a live bait (anchovy) tank. This requires a 30 Gallon plastic rain drum with water flowing in one circular direction to create the needed "current" to make the tuna bait happy. If anchovies are not swimming against current they will die.

I am guessing around 2 MPH in a circular motion. This will be created by a water pump hooked into a pipe that is mounted vertically in the drum with holes drilled in one side on the pipe hence creating the current.

My question: Is there a formula for figuring out the needed GPH pump, vertical pipe size, and size needed for the holes in the pipe?
 
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I'm having trouble picturing the tank- presumably water also drains out?

2 miles per hour = 0.9 m/s (more sensible units), and this velocity is basically uniform- if it's the speed of fluid coming out of the hose, and the hose is of reasonable size compared to the tank, you can set up a swirling flow with this speed.

Say you are using a 1" hose: 0.0005 m^2 of area, 1 m/s flow rate = 0.0005 m^3/s volumetric flow = 8 gallons/minute.

That's a rough estimate-YMMV.
 
Just like a 50 gallon drum, but smaller 30 gallon. and I am assuming that the holes size drilled pipe matter too?
 
kck said:
I am assuming that the holes size drilled pipe matter too?

Again, I am having a hard time picturing what you have in mind.
 
Looked for "water flow chart" and found this which might be a start:
http://flexpvc.com/WaterFlowBasedOnPipeSize.shtml

The length, diameter, and resistance of the pipe are important and probably best estimated heuristically. I did some calcs based on our Fire Dept flow charts for different hoses and pumps -- which are way out of your range but might be indicative:
200 feet of hose with a TFT nozzle will run 125 gpm at:
125 psi for 1-3/4" hose
100 psi for 2-1/2" hose
600 feet of 3" supply hose will deliver 125 gpm at about 28 psi
 

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