does 3/4" + 3/4" = 1 1/2"?

[tomheo]

Hey all,

I'm looking to replace my two Mak4's with a Dolphin Aqua Sea Ampmaster 2700. The Mak4's have 3/4" outlets/inlets. I wanted to know if I have the two 3/4" bulkheads from my sump going to one 1 1/2" fitting, will that in effect be similiar to just having a 1 1/2" bulkhead? Mathematically it seems to make sense to me, but it seems like something shouldn't work.

I'd rather not drill a new hole into my sump (especially since I can't take it out of the stand w/o emptying the tank, making the drilling process not so fun).

Thanks!

P.S. I'd be making a manifold for the outlet with some 3/4" fittings going to two opposing Sea Swirls and a chiller.

 

[Jrsydevi1]

I'm not a math guy or geometry guy, but I AM a plumber, and I can tell you that one 1 1/2" pipe carries MUCH more water than two 3/4 inch pipes will..

If I'm not mistaken, i beleive an 1 1/2" carries almost 4x the volume of a 3/4..

 

[2poor2reef]

I'm not a math guy OR a plumber but I do eat peppermint patties and I can tell you for sure that there's more peppermint in a 1 1/2 inch in diameter patty than in two 3/4 inchers put together. Wait... I want to test that again.

 

[2poor2reef]

My mistake. This calculation has to do with pie, not peppermint patties.

 

[afss]

by my calcs the cross sectional area of a 1.5 is app 1.76. it is .88 for 2 * .75 inche pipes. That makes it almost exactly twice the area, so i would think that it should flow approximately twice the volume. I am sure there are other factors that come into play with the flow rates, but i would guess that twice the volume would be pretty close.

 

[Nostrathomas]

to find volume of a cylindrical object=0.785xdia2xlength Use this formula.Hope this helps.nostra

[ July 08, 2001: Message edited by: Nostrathomas ]

 

[Reef Engineer]

Without getting into too many specifics, there is a formula (Hazen-Williams Formula) that is widely accepted for the calculation of pipe flow (especially for water utilities). This formula states:

Q = 0.432 * C1 * D(raised to the power 2.63) * S (raised to the power 0.54)

where:

Q = discharge in ft3/sec
0.432 = unitless coefficient
C1 = coefficient based on surface roughness
D = pipe diameter in ft
S = frictional head loss

Since all the variables would essentially remain the same (same material, same head loss, etc), the only thing that would change would be the diameter so you can see that there is a big difference between a 3/4" pipe and a 1.5" pipe (the above would need to be sized down to inches, obviously) As a guide, though, a 1" pipe would have ~2 times the Q of a 3/4" pipe so the difference between a 3/4" and a 1.5" would be that much greater.

Remember, we are looking at flows not simple volumes.

Randy

[ July 08, 2001: Message edited by: Reef Engineer ]

 

[Jrsydevi1]

yeah.. thats what I meant...

 

[Reef Engineer]

I know - just filling in the blanks for ya.

It's been awhile since I've had to do pipe flow calculations but I do know where to find the formulas.

Randy

 

[Nostrathomas]

[ July 09, 2001: Message edited by: Nostrathomas ]