gpm

how many gpm from 1.25 inch pipe with 17 psi or 1.5 ich pipe with 17psi

You can't do a google search yourself ?

What kind of pipe? Is that the nominal size or the actual i.d.? Is the interior smooth or rough? How long is the pipe? Size and pressure are the simplest parts of the equation.

Funny how this same question in various forms has spilled onto four threads here.

There are multiple variables that all need to be taken into account. All these variables are listed and graphed in the appendix of the IPC and the UPC and all other nationally recognized code books. It ain't rocket science but it does take time to get all the figures straight. Like HJ said. At what pressure, in what pipe, how long is the pipe, how far above sea level.

vandal said:

how many gpm from 1.25 inch pipe with 17 psi or 1.5 ich pipe with 17psi

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You cannot solve this problem unless you know your velocity. Just think, you could have 17psi line pressure and the valve is closed ... that equals zero GPM in both pipes.

99k said:

You cannot solve this problem unless you know your velocity. Just think, you could have 17psi line pressure and the valve is closed ... that equals zero GPM in both pipes.

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Velocity is just an arithmetic conversion of GPM, not another variable that's needed to be supplied. Part of the concept of how much will flow from something is an assumption that there is an unrestricted opening to flow out of. Otherwise, the restriction has to be stated. Your example contradicts that assumption, and so merely answers the question of how much will flow through a closed valve, regardless of any other variable.

vandal said:

how many gpm from 1.25 inch pipe with 17 psi or 1.5 ich pipe with 17psi

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For plastic pipe 116' long, losing 17 psi in pressure,
1-1/4" ID pipe @ 40 gpm or 1-1/2" ID pipe @ 60 gpm

vandal said:

how many gpm from 1.25 inch pipe with 17 psi or 1.5 ich pipe with 17psi

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More variables involved. What is the length of the pipe? Where is the 17PSI measured?

I have 300 gallon storage tank with 40ft of fall. That's how I got 17 psi. I only want to know gpm of water through smooth plastic pipe id 1.25 and 1.5 inch at end of 40 ft. I did Google search but got all kinds of conflicting answers thought I would ask the experts.

vandal said:

I have 300 gallon storage tank with 40ft of fall. That's how I got 17 psi. I only want to know gpm of water through smooth plastic pipe id 1.25 and 1.5 inch at end of 40 ft. I did Google search but got all kinds of conflicting answers thought I would ask the experts.

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You have what's called a "gravity tank."

This might work
http://www.engineeringtoolbox.com/bernouilli-equation-d_183.html

"Example - outlet velocity from a vented tank
The outlet velocity of a tank with height 10 m can be calculated as
V2 = (2 (9.81 m/s2) (10 m))1/2
= 14 m/s"

40'=12.2 m, so the velocity is 15.5 m/s = 50.8 ft/sec = 610 in/sec.
1.25" ID pipe = 1.23 sq. in. area and 1.77 sq. in for the larger pipe.
This is 0.434 cu ft/sec and 0.768 cu ft./sec

http://www.onlineconversion.com/volume.htm
There are 7.48 gals/cu ft, so 3.25 gals/sec and 5.75 gals/sec gives you 195 gpm and 345 gpm.

I'd check this. . .I've never done this experiment! With the smaller pipe your 2500# of water should empty in 39 sec. Using a smaller ID 40' garden hose and scaling the numbers will tell you how close this formula gets you.

tank

In that case you have introduced another variable because you will only have 17psi when the tank is full. As soon as the water level starts to drop, so will the pressure.