# pvc pipe size question

• posted on March 6, 2005, 12:57 am
Hi there:
Sorry for intruding but can I ask a question. Can someone tell me please how much water roughly will travel through PVC 40 pipe by gravity (no pump), if it's vertical (roughly) and only about 6 ft high? In a few different diameters? I've looked on the internet and I can only find tables of friction loss and tables of maximum flow rates. I just want to get an idea for an aquarium system that I'm building. i.e. with 1/2", 1", 1.5", etc.
I appreciate any and all help. Quietreef
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• posted on March 6, 2005, 3:04 am
"quietreef"
I don't think plumbers would know this. Try looking for "'alt.physics" or something.
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• posted on March 9, 2005, 5:55 am
On Sun, 06 Mar 2005 00:57:34 +0000, quietreef wrote:

The formula for figuring volume of a cylinder is 2 pi r squared times height.
In the case of 1/2" inch pipe 72 inches high that would be (2 x 3.14 x .25squared) x 72. Which would give you 28 1/4 cubic inches. 1 gallon(US) is 231 cubic inches. So that would give you .1223 of a gallon, or about a pint.
That's how much water it will hold. How much water will travel through the pipe depends on whether it will be at full volume for the pipe and how long a period of time you are looking at. For a 6' length of pipe, friction loss is minimal for an aquarium.
Are you asking how long for a certain amount of water, or how much water in a certain amount of time?
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• posted on March 9, 2005, 3:43 pm
Hi there:

I'm looking for rate. If the water is falling by gravity with no pump or back pressure, roughly, how many gallons/hour will I get in a 1/2" pipe or a 1" pipe, which I assume is 2X whatever the 1/2 number is. Now that you've laid it out so nicely, I should be able to figure it out, thanks.
quietreef
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• posted on March 10, 2005, 9:53 pm

You mixed up the formula. It is pi r squared NOT 2 pi r squared. 2 pi r is for circumference.
You need a different formula to figure out the flow rate anyway (but you willuse this calculation also). You need the pressure of the water. In a vertical pipe you get 1 PSI of pressure for every 2.33 feet of head (height). You'd be at about 2.5 PSI at 6' (without a calculator). I am still looking for this formula, but if will give you cuft/sec. Then you can use 7.48 gal/cuft of water to calculate gal/sec.
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• posted on March 11, 2005, 3:16 am
"Eric G."
Hey, by this time, he could have built the stupid thing, bought the pipe in several sizes, and timed it by himself.
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• posted on March 11, 2005, 2:59 pm
Yeah, I think I'll probably just do this. It's easy enough to time it myself, but thanks anyway.
Quietreef

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• posted on March 11, 2005, 8:52 pm

I never said I was quick :-)
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• posted on March 12, 2005, 6:27 pm
I have held off on this post because it is soo stupid. Fill the god damn tub and time it darining dont build a thing. There are groups dedicated to fish tank systems.