Maintaining a constant volume of water in a tank

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Discussion Overview

The discussion revolves around maintaining a constant volume of water in Tank A while water drains into Tank B and is subsequently pumped back to Tank A. Participants explore the relationship between the flow rate, hole diameter, and water height, considering practical applications and potential issues in the system design.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests determining the diameter of the hole based on a known pump rate of 19 liters per minute, assuming a velocity of 1.
  • Another participant questions the relevance of the height that gives a velocity of 1, indicating that the flow rate may depend on the height of the water above the hole.
  • A participant proposes closing off the valves in the system to maintain water levels, but later clarifies that the system cannot be sealed due to the open top of Tank A and the variable water level in Tank B.
  • Suggestions are made for using an open trough or direct pumping from Tank A to simplify the system, with concerns about the potential for Tank B to run dry.
  • One participant emphasizes the importance of pressure in determining flow rates and suggests using pipe diameter calculators, noting that back pressure from a filter could affect pump performance.
  • A request is made for a diagram to clarify the arrangement of tanks, pipes, and pumps to facilitate analysis of the problem.

Areas of Agreement / Disagreement

Participants express differing views on the best approach to maintain constant water volume, with no consensus on the optimal design or solution. Some propose practical modifications while others focus on theoretical aspects of flow and pressure.

Contextual Notes

Participants acknowledge the need for clarity regarding the arrangement of tanks, pipes, and pumps, indicating that assumptions about system design may affect the analysis. There are also concerns about the implications of variable water levels and the potential for evaporation affecting Tank B.

KatelynG
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I have water draining from a tank A into a tank B through a hole (or short pipe) and then being pumped back from B to A. If I know the rate of the pump (say 19 liters per minute), what should the diameter of the hole be so that the volume of tank A remains the same? The actual volume of A is arbitrary, so I've started with the assumption that I'll use whatever height gives me a velocity of 1.
 
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KatelynG said:
I have water draining from a tank A into a tank B through a hole (or short pipe) and then being pumped back from B to A. If I know the rate of the pump (say 19 liters per minute), what should the diameter of the hole be so that the volume of tank A remains the same? The actual volume of A is arbitrary, so I've started with the assumption that I'll use whatever height gives me a velocity of 1.
Welcome to the PF.

Weird problem. Can you give us some context? I'd just close off the valves in the system so the levels stay the same.
 
Doesn't it depend on the height of the water above the hole? I'm not sure what you mean by the height that gives a velocity of 1 ...
 
berkeman said:
Welcome to the PF.

Weird problem. Can you give us some context? I'd just close off the valves in the system so the levels stay the same.

I'm constructing a fountain of sorts. The idea is that water flows from Tank A to Tank B, then through a filter and then is pumped back to Tank A. Tank A has an open top, and Tank B has a variable amount of water in it, so I can't seal off the system and pull a vacuum.
 
votingmachine said:
Doesn't it depend on the height of the water above the hole? I'm not sure what you mean by the height that gives a velocity of 1 ...
The equations I started with used the velocity of the water, which is dependent on the volume (height, depth...) of the water, but that's what I'm attempting to maintain as a constant...
 
float valve?
 
The easy answer for home construction purposes is an open trough at the top of tank A, that can handle any flow amount into tank B (it simply pours by overflow into B). Or put the pump on an outlet from tank A directly. It sounds like tank B is an extraneous reservoir for filtering purposes. If so then pump from the bottom of A, thru a filter, and back into the top of A.

The flow rate depends on the pressure. You can google and find pipe diameter calculators, but the pressure matters. It matters to the pump also. As the filter gets occluded, the pump will pump at lower flow rates from the back pressure building.

An overflow pipe (like in the back of a toilet tank) will allow tank A to fill, and then handle the variable flow into it with a variable flow out. I don't like the possibility of running tank B dry though, if evaporation happens. Your pump will burn up. Tank B could have a float valve on a water supply, to keep it safe.
 
KatelynG said:
I have water draining from a tank A into a tank B through a hole (or short pipe) and then being pumped back from B to A. If I know the rate of the pump (say 19 liters per minute), what should the diameter of the hole be so that the volume of tank A remains the same? The actual volume of A is arbitrary, so I've started with the assumption that I'll use whatever height gives me a velocity of 1.

This problem should not be too difficult to analyse .

We need to be clear about the actual arrangement of the tanks , pipe and pump though . Can you post a diagram ?
 

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