# Inches of Water Column
**URL:** https://boards.straightdope.com/t/inches-of-water-column/315245
**Category:** Factual Questions
**Created:** [August 2, 2005, 2:20am UTC](https://boards.straightdope.com/t/inches-of-water-column/315245 "2005-08-02T02:20:10Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [August 2, 2005, 2:20am UTC](https://boards.straightdope.com/t/inches-of-water-column/315245/1 "2005-08-02T02:20:10Z")
When one speaks of inches of water column, the diameter of that water column doesn’t really matter, does it? If P = pgh (where p=density) and P = F/A, then because pressure is per unit area…the diameter of that water coumn doesn’t matter, right?
So, whether a 5-ft column of water in a pipe or 5-ft column of water in a 55-gal drum, the water pressure at the bottom is the same, correct? (Note: 1 psi = 2.31 ft x 12 in/ft = 27.72 in)
- Jinx
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### Author:  [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)
#### Post date: [August 2, 2005, 2:26am UTC](https://boards.straightdope.com/t/inches-of-water-column/315245/2 "2005-08-02T02:26:56Z")
The short answer is no, the diameter doesn’t matter.
The long answer is that some people will nitpick over things like surface tension, wetting, the meniscus, quantum effects, and such.
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### Author:  [@Squink](https://boards.straightdope.com/u/Squink)
#### Post date: [August 2, 2005, 3:04am UTC](https://boards.straightdope.com/t/inches-of-water-column/315245/3 "2005-08-02T03:04:53Z")
I saw a mill pond in Connecticut a few years back where the damn had been modified to make the reservoir a bit deeper. On a 50 foot wide dam, they ran a string of 2X10’s flat across the top, bolted them on, and nailed some more 2X10"s perpendicular to the first set. It worked. The pond was hundreds of feet long.
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### Author:  [@Xema](https://boards.straightdope.com/u/Xema)
#### Post date: [August 2, 2005, 3:10am UTC](https://boards.straightdope.com/t/inches-of-water-column/315245/4 "2005-08-02T03:10:40Z")
> [@Jinx](#):
>
> So, whether a 5-ft column of water in a pipe or 5-ft column of water in a 55-gal drum, the water pressure at the bottom is the same, correct?
Basically, yes. And when you go Scuba diving, the pressure you encounter at a certain depth does not depend on the size of the lake.
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### Author:  [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)
#### Post date: [August 2, 2005, 3:59am UTC](https://boards.straightdope.com/t/inches-of-water-column/315245/5 "2005-08-02T03:59:20Z")
If the diameter of the tank made a difference then [something like this ought to work.](http://pg.photos.yahoo.com/ph/dwsimm2000/detail?.dir=8cf7&.dnm=b1a8.jpg&.src=ph)
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### Author:  [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)
#### Post date: [August 2, 2005, 4:29pm UTC](https://boards.straightdope.com/t/inches-of-water-column/315245/6 "2005-08-02T16:29:36Z")
**Jinx** , your profile lists your occupation as Engineering. Care to clarify what sort of engineering?