What happens to a pump's pressure gauge if you disconnect a hose line

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Discussion Overview

The discussion centers around the behavior of a pump's pressure gauge when a hose line is disconnected. Participants explore the implications of this action on pressure readings and flow rates, considering both theoretical and practical aspects of pump operation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that disconnecting the hoseline would lead to a lower gauge reading, potentially approaching 0, as the outlet would be at atmospheric pressure.
  • Another participant proposes that the gauge pressure would decrease while the water flow would increase, indicating a relationship between flow and pressure in this scenario.
  • Concerns are raised about the validity of AI-generated information, with a participant emphasizing that such sources should not be considered authoritative in technical discussions.
  • Questions are posed regarding whether the flow will increase or decrease upon disconnection, and how this relates to the type of pump used.
  • There is a query about whether removing the hose and nozzle connects the pump output directly to atmospheric pressure, which could affect gauge readings.

Areas of Agreement / Disagreement

Participants express differing views on the expected behavior of the pressure gauge and flow rates upon disconnection of the hose. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Participants note the importance of manufacturer data and testing for understanding pump behavior under different conditions, suggesting that empirical evidence may be necessary to clarify the discussion.

David43214
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New user has been reminded not to try to use AI chatbots as references in the PF technical forums
TL;DR
Would the pressure go up or down?
Imagine a firetruck with a hoseline attached to the pump. The pump is set to 800kpa with 100kpa loss due to friction in the 30m hoseline so you have 700kpa at the nozzle.

What would the pump's gauge read if you disconnected the hoseline?

I thought since there is no more resistance, the pressure gauge would show a much lower reading, maybe 0 because the pump's outlet is now at atmospheric pressure.
However, ChatGPT was telling me the gauge jumps to the static (deadhead) pressure of the pump.
 
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David43214 said:
I thought since there is no more resistance, the pressure gauge would show a much lower reading, maybe 0 because the pump's outlet is now at atmospheric pressure.
I believe that you are correct: the gauge pressure would go down, while the waterflow would increase.
A chart for that particular pump should tell you what the manufacturer has recorded from the tests completed for different conditions.
 
Welcome to PF.

David43214 said:
However, ChatGPT was telling me the gauge jumps to the static (deadhead) pressure of the pump.
Please keep in mind that AI chatbots are not considered valid references in the technical PF forums. Thanks.
 
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Will the flow increase or decrease?
If the flow increases, does that mean the pressure falls?
Does it depend on the type of pump being used?
Does removal of the hose and nozzle restriction, connect the pump output with the gauge, directly to atmospheric pressure?
 
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