# Liquid pressure differential gage?

**URL:** <https://boards.straightdope.com/t/liquid-pressure-differential-gage/1015221>\
**Category:** Factual Questions\
**Created:** [March 6, 2025, 8:34pm UTC](https://boards.straightdope.com/t/liquid-pressure-differential-gage/1015221 "2025-03-06T20:34:03Z")\
**Posts on this page:** 5\
**Page:** 2

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**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\
**Post date:** [March 12, 2025, 9:11pm UTC](https://boards.straightdope.com/t/liquid-pressure-differential-gage/1015221/21 "2025-03-12T21:11:26Z")

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> [@ZurBob](#):
>
> **Be aware** if you exceed 3psi you’ll blow the guts out of this meter!

I bought the $39.00 one. Let you know how it works out

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**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\
**Post date:** [March 13, 2025, 2:51pm UTC](https://boards.straightdope.com/t/liquid-pressure-differential-gage/1015221/22 "2025-03-13T14:51:38Z")

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> [@HoneyBadgerDC](#):
>
> I bought the $39.00 one. Let you know how it works out

It came with about an eight inch hose. I used one of my hoses so I could see it which was 72" long. All my readings seem like they are light. I wonder if the long hose is throwing off the readings If it stops raining I will try to rig the short hose where I can see it.

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**Author:** ![ThisOneGuy](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@ThisOneGuy](https://boards.straightdope.com/u/ThisOneGuy)\
**Post date:** [March 13, 2025, 4:34pm UTC](https://boards.straightdope.com/t/liquid-pressure-differential-gage/1015221/23 "2025-03-13T16:34:54Z")

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Hose length shouldn’t matter if the pressure changes are slow enough (they propagate at the speed of sound in the tube, so slow enough is pretty fast). Leaks in the connections would matter.

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**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\
**Post date:** [March 13, 2025, 6:31pm UTC](https://boards.straightdope.com/t/liquid-pressure-differential-gage/1015221/24 "2025-03-13T18:31:38Z")

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Or if your extension hose is so flimsy that its cross-section expands and contracts with changing pressure. Not real likely at ~2 psi, but not impossible either.

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**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\
**Post date:** [March 20, 2025, 9:03pm UTC](https://boards.straightdope.com/t/liquid-pressure-differential-gage/1015221/25 "2025-03-20T21:03:43Z")

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> [@ThisOneGuy](#):
>
> …pressure changes…propagate at the speed of sound in the tube…

I worked many years in the biz, and am embarrassed to admit this is a new one on me.  
Thanks for the enlightenment!

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