# Pipe Volume Math Question

Discussion in 'Computer Support' started by Jimi, Mar 18, 2007.

1. ### JimiGuest

Hello,

I am filling a pipe with glycol.. The pipe is 1/2" (inside diameter).
I need to know how many imperial gallons per 100 feet this pipe will hold so
I can figure out how much glycol to buy.
Thanks for any help on this. Jim

Jimi, Mar 18, 2007

2. ### SJPGuest

3.397301 Gallons

SJP, Mar 18, 2007

3. ### RobbGuest

Ask a scientist, or try this formula.
--

Question From:
Sammy, Age 8.

My Dad and I are going to build a sail boat using PVC pipes for flotation.
Is there an easy way to caculate how many 8 foot long, eight inch diameter
pipes we will need to support our weight and keep the boat floating?

The weight that the pipes will support is the weight of the water they can
displace minus the weight of the pipes themselves. To calculate this, you
need to know the volume of the pipes, the weight of the pipes, and the
density (weight/volume) of water.

Fresh water has a density of 1 kg/liter. Salt water has a higher density.
The volume of the pipes can be calculated from their diameter and length
by the formula

V = L pi r^2, where
L is the length of the pipe, 8 ft = 96 in.,
pi = 3.14159,
r is the radius of the pipe, 4 in.

So the volume of a pipe is

V = (96 in)(3.14)(4 in)^2
= (96 in)(3.14)(16 in^2)
= 4823 in^3

Now you need to convert cubic inches to liters. 1 cubic inch = 0.01639
liters, so

V = (4823 in^3)(0.01639 L/in^3)
= 79 L.

So, in fresh water, an 8-ft length of 8-in diameter PVC pipe can float 79
kg minus its own weight.

[attrib lost, from the 'net]

Robb, Mar 18, 2007
4. ### Old GringoGuest

http://www.inter-mountain.com/Pipe_Related_Formulas.htm

Old Gringo, Mar 18, 2007
5. ### WhiskersGuest

First-form maths!

The volume of a cylinder (a pipe is a cylinder) is (22*r*r*h)/7 where r is
the radius (half the diameter) and h is the height (or length, if you
like), and 22/7 is pi. Make sure that you use the same units (either feet
or inches) for both radius and height!

1 imperial gallon is 277.4193 cubic inches or 0.160544 cubic feet.

Whiskers, Mar 18, 2007
6. ### Geoff PearsonGuest

It is amazing that anyone does these calculations in imperial measure now.

Geoff Pearson, Mar 18, 2007
7. ### Mike EasterGuest

Numerator = cross-sectional area of pipe cm^2 x pipe length cm x ImpGal
Denominator = conversion units for ImpGal cm^3

Values: 0.5 " ID = 0.25" radius = .635 cm
Xsec = pi x r^2 = pi x .635^2 cm^2

100' = 30480 cm = 3 x 10^4 cm
ImpGal = 4546.09 cm^3 = 4.546 x 10^3 cm^3

Numerator = pi x .635^2 x 3.048 x 10^4 cm^3 x ImpGal
Denominator = 4.546 x 10^3 cm^3

I get 8.49 Imp Gal

It seems like 100 feet of 1/2 inch pipe could hold something less than
10 gallons of liquid.

Mike Easter, Mar 18, 2007
8. ### philoGuest

but i'd purchase 3.397302 gallons , just to be on the safe side.

I think it's a school math problem though

philo, Mar 18, 2007
9. ### WhiskersGuest

Perhaps he's got these old pipes and hasn't heard that shops now have to
sell stuff in litres?

Whiskers, Mar 18, 2007
10. ### WhiskersGuest

I think you let your decimal point slip a bit somewhere in there.

My method:

22*.25*.25*1200/7=235.7142857142857143 cubic inches

235.7142857142857143/277.4193=0.8496679420439951881 imperial gallons

Whiskers, Mar 18, 2007
11. ### SJPGuest

I've changed my mind on my previous answer and reckon its 0.8493253 Gallons

SJP, Mar 18, 2007
12. ### Mike EasterGuest

I'm trying to figure out why anyone would be filling 100 feet of 1/2"
pipe with glycol, presumably ethylene glycol.

Mike Easter, Mar 18, 2007
13. ### Mike EasterGuest

1 cm of that pipe will hold 1.27 cc, that sounds right, and a meter 127
cc and 30 meters would be 3810 cc, so I think your answer is better than
mine. I must've misplaced a decimal somewhere.

Mike Easter, Mar 18, 2007
14. ### Mike EasterGuest

Aha! There it is. 100' = 3048 cm = 3 x 10^3 cm
pi x .635^2 x 3.048 x 10^3 cm^3 x ImpGal
Now it gets 0.849

Mike Easter, Mar 18, 2007
15. ### Mike EasterGuest

Right there.
That sounds pretty close. ;-)

Mike Easter, Mar 18, 2007
16. ### RobbGuest

Then is my volume calculator borkd?
I get 235.62 cubic inch = 0.849324351255694 gallon [UK]

Robb, Mar 18, 2007
17. ### WhiskersGuest

To stop it from freezing?

Whiskers, Mar 18, 2007
18. ### WillardGuest

Willard, Mar 18, 2007
19. ### JimiGuest

Jimi, Mar 18, 2007
20. ### WhiskersGuest

Copy/paste from Kcalc; odd when being lazy makes it easier to get answers
to a silly degree of precision than to get a rough aproximation. Let's
say 'a bit less than 4 litres' to keep things sane )

My value for pi is approximately 0.04% on the high side - but it's better
to have a drop left over than being a drop short, and differential thermal
expansion and manufacturing variations are probably going to swamp that
margin.

Whiskers, Mar 18, 2007