stupid plumbing question

[CHOMPERS]

The pipe size to areas are as follows:

size __area
1/2 = .1963
3/4 = .4418
1.0 = .7854
1.25= 1.227
1.5 = 1.767
2.0 = 3.142

You would use two 3/4" pipes to divide the flow from a one inch pipe.

 

[CHOMPERS]

In the top middle circle with the two inner circles, the two smaller circles are half the diameter of the larger outer circle. The larger circle clearly has more area then the two circles of half its diameter. This is why you have to use the area rather than the diameters in your calculations.

 

[SpeshulEd]

I appreciate the amount of math being used in this thread! Totally awesome!

And we wondered when we'd ever use this stuff!

 

[whodey]

IF you have 1.5" pipe from the discharge side of the pump and split it as close to its final destination as possible into two 3/4" pipes, unrestricted, the pump theoretically would still be pumping through one 1.5" pipe. Even if you split that 1.5" four ways as long as all the diameters added up to 1.5", or close to it.

You may want to check your math on that one. Two .75" pipes will not equal the cross sectional area, and therefore flow rate, of one 1.5" pipe.

Imagine any diameter circle, a pipes cross sectonal image. Then superimpose on that image 2 circles that have half the diameter of the firs pipe, side by side. Note that these two smaller circles dont completely cover the large single cirlce. Pic below.

By the numbers:
Area of a circle;
A= (pi)*(r)(r)

Assume the larger pipe is 4" in diameter
thus A=3.14*2*2
A=12.56 sq in

Assume 2 smaller pipes at 2" in diameter
Thus 2*A= (pi)*(r)(r)
A=3.14*1*1
A= 3.14
2A=6.28

the resulting area is only half of the initial larger pipe. IE The same total diameters never equal the same cross sectional area.

Now, Using four .75" pipes will result in roughly the same area as one 1.5" pipe.

For the math illiterate see the pic. The cylinder voumes aren't the same.