Return pipe diameter/head loss Q?

reef_doug · 10/19/2006, 12:03 AM

Tank is a 180r, return pump Eheim 1262 Internal w/ 3/4" out.

I'm looking at the headloss calculator and it shows less head loss with 1" but somewhere I read the larger diameter pipe could add something to slow down the flow. head loss calculator

Output will be a single pipe up then "Y" off to two 3/4" loc-line outputs.

Should my return plumbing up to the "Y" be 3/4" or 1"?

TIA,
Doug

Ken668 · 10/19/2006, 05:04 AM

Use the 1" as this will give you less head loss and therefore more flow. If you use 1" for your outlet, the velocity will be less. If anything, I would use 1" all the way (even after Y), then use a reducer right at the output to drop it to 3/4" to get some more velocity.

ChemE · 10/19/2006, 05:05 AM

Quote:

Originally posted by reef_doug
...I'm looking at the headloss calculator and it shows less head loss with 1" but somewhere I read the larger diameter pipe could add something to slow down the flow...

I have seen a few people here try to defend this notion by making reference to "water weight". This is of course utter nonsense. Simple hydrodynamics tells us that the larger the diameter of a pipe the less the dynamic head loss experienced by pumping through said pipe. Diameter has no effect on static head.

hillk · 10/19/2006, 06:36 AM

Oh yea take a 6 ft 1 inch pipe fill with water and point it in the air and try to blow the water out and then take a 6ft piece of half or quarter inch and blow which is easier? You will drowned with the one in pipe trying to push it up and out

RicksReefs · 10/19/2006, 07:26 AM

sorry bud, but that has nothing to do with anything concerning fluid hydraulics. a half inch diameter of water weighs the same everytime, whether it's in a 1/2" pipe or a 10" pipe.

hillk · 10/19/2006, 09:43 AM

no it doesn't that does not make any sense. if you had a 10 in return pipe the pump wont push it

bvanhoveln · 10/19/2006, 10:14 AM

Sorry hillk - Rick is correct

The principle is pretty simple - water pressure has nothing to do with the amount of water, depth is the only factor. The example you gave is incorrect - it would actually take more force to push the 6ft water depth out of the 1/2 inch pipe (or even a stirring straw) than it would on the 1 inch pipe (or even one the size of a basketball) as there are losses due to drag on the pipe.

please read the following from Wikipedia - but there are many other good sources as well.

Hydrostatic pressure

In the case where the fluid is at rest, called fluid statics or hydrostatics (from hydro meaning "water" and static meaning "at rest"), the force is the gravitational force acting on the mass of fluid above the measurement point. The resulting hydrostatic pressure (static pressure) is isotropic: the pressure acts in all directions equally, according to Pascal's law:

p = \rho g h\,

where:

* ρ (rho) is the density of the fluid (the practical density of fresh water is 1000 kg/m3);
* g is the acceleration due to gravity (9.8 m/s2 );
* h is the height of the water column in metres.

For example, assume a water column 1 metre high. The pressure at the bottom of the column will be

p = \rho g h = 1000 \cdot 9.8 \cdot 1 = 9800 Pa. We see that the pressure increases linearly with the water depth; a depth of 2 metres would yield a pressure of 19600 Pa, a depth of 3 metres would yield a depth of 29400 Pa, and so on

Hope this helps

reef_doug · 10/19/2006, 11:03 AM

Quote:

Originally posted by Ken668
Use the 1" as this will give you less head loss and therefore more flow. If you use 1" for your outlet, the velocity will be less. If anything, I would use 1" all the way (even after Y), then use a reducer right at the output to drop it to 3/4" to get some more velocity.

Thanks, I'm going to use Ken668's idea with 1" all around, and then 3/4" reducer to loc-line at the ends.

Best
Doug

UCanDoIt · 10/19/2006, 11:20 AM

That's what I would suggest. My aquarium techician has his reef tank setup that way, 1" up to a Ocean Motion device and then 4-way 3/4" coming out and the flow with his Eheim 1260 is impressive. I have 5/8" coming out of mind all the way to the top where it splits off into 2x 3/4" and it is noticeably slower and less waterflow than his and his setup is a foot taller than mine.

sjm817 · 10/19/2006, 11:57 AM

Ever wonder why Fire Hoses dont look like long coffee stirrers?

ChemE · 10/21/2006, 01:13 AM

Ever wonder why so many people on Reef Central lack basic science and reasoning skills?

10/19/2006, 12:03 AM	#1
reef_doug Premium Member Join Date: Jul 2006 Location: Hesperia/Apple Valley Posts: 3,814	Return pipe diameter/head loss Q? Tank is a 180r, return pump Eheim 1262 Internal w/ 3/4" out. I'm looking at the headloss calculator and it shows less head loss with 1" but somewhere I read the larger diameter pipe could add something to slow down the flow. head loss calculator Output will be a single pipe up then "Y" off to two 3/4" loc-line outputs. Should my return plumbing up to the "Y" be 3/4" or 1"? TIA, Doug __________________ "If you have more than one tank in your livingroom, you might be a reefneck" Current Tank Info: 180r SoCal Creations, 75g SCC1M Sump, WM EcoBAK, NextReef SMR1, TropicMarin Salt, ACIII, 3x250w HQI Phoenix 14k, 2x140w Super Actinics, ATi BM250, Eheim 1262, Tunze 2x6100+7095, Tunze Osmolator, 6 stage RODI w/ Spectrapure MaxCap

10/19/2006, 06:36 AM	#4
hillk Registered Member Join Date: Sep 2006 Location: Bloomington In Posts: 24	Oh yea take a 6 ft 1 inch pipe fill with water and point it in the air and try to blow the water out and then take a 6ft piece of half or quarter inch and blow which is easier? You will drowned with the one in pipe trying to push it up and out __________________ hillk Current Tank Info: 90 gal salt water cycling

10/19/2006, 09:43 AM	#6
hillk Registered Member Join Date: Sep 2006 Location: Bloomington In Posts: 24	no it doesn't that does not make any sense. if you had a 10 in return pipe the pump wont push it __________________ hillk Current Tank Info: 90 gal salt water cycling

10/19/2006, 11:57 AM	#10
sjm817 On Yer left! Join Date: Sep 2004 Location: Northern VA Posts: 18,777	Ever wonder why Fire Hoses dont look like long coffee stirrers? __________________ - Scott

10/21/2006, 01:13 AM	#11
ChemE Registered Member Join Date: Aug 2005 Location: East Nashville, TN Posts: 1,607	Ever wonder why so many people on Reef Central lack basic science and reasoning skills? __________________ Holding it down on the engineering tip y'all Current Tank Info: 190G

10/19/2006, 05:04 AM	#2
Ken668 Registered Member Join Date: Oct 2004 Location: Albany, NY Posts: 832	Use the 1" as this will give you less head loss and therefore more flow. If you use 1" for your outlet, the velocity will be less. If anything, I would use 1" all the way (even after Y), then use a reducer right at the output to drop it to 3/4" to get some more velocity.

10/19/2006, 07:26 AM	#5
RicksReefs Moved On Join Date: Apr 2002 Location: In America's Dangling Junk State. Posts: 6,413	sorry bud, but that has nothing to do with anything concerning fluid hydraulics. a half inch diameter of water weighs the same everytime, whether it's in a 1/2" pipe or a 10" pipe.

10/19/2006, 10:14 AM	#7
bvanhoveln Registered Member Join Date: Aug 2006 Location: Mt. Pleasant, WI Posts: 108	Sorry hillk - Rick is correct The principle is pretty simple - water pressure has nothing to do with the amount of water, depth is the only factor. The example you gave is incorrect - it would actually take more force to push the 6ft water depth out of the 1/2 inch pipe (or even a stirring straw) than it would on the 1 inch pipe (or even one the size of a basketball) as there are losses due to drag on the pipe. please read the following from Wikipedia - but there are many other good sources as well. Hydrostatic pressure In the case where the fluid is at rest, called fluid statics or hydrostatics (from hydro meaning "water" and static meaning "at rest"), the force is the gravitational force acting on the mass of fluid above the measurement point. The resulting hydrostatic pressure (static pressure) is isotropic: the pressure acts in all directions equally, according to Pascal's law: p = \rho g h\, where: * ρ (rho) is the density of the fluid (the practical density of fresh water is 1000 kg/m3); * g is the acceleration due to gravity (9.8 m/s2 ); * h is the height of the water column in metres. For example, assume a water column 1 metre high. The pressure at the bottom of the column will be p = \rho g h = 1000 \cdot 9.8 \cdot 1 = 9800 Pa. We see that the pressure increases linearly with the water depth; a depth of 2 metres would yield a pressure of 19600 Pa, a depth of 3 metres would yield a depth of 29400 Pa, and so on Hope this helps

10/19/2006, 11:20 AM	#9
UCanDoIt Moved On Join Date: Mar 2006 Location: Bay Area CA Posts: 1,684	That's what I would suggest. My aquarium techician has his reef tank setup that way, 1" up to a Ocean Motion device and then 4-way 3/4" coming out and the flow with his Eheim 1260 is impressive. I have 5/8" coming out of mind all the way to the top where it splits off into 2x 3/4" and it is noticeably slower and less waterflow than his and his setup is a foot taller than mine.