water restriction question

xsdbs

xsdbs

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Oct 16, 2006
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I am curious about water flow being restricted in plumbing where 90's are used vs 45's ( angles ). I am in the process of re plumbing some of my tank today and I know that a straight line is probably best but I will need to add a couple 90's and well , was curious about this. Thanks in advance for any info on this.
 
Keep in mind all restrictions result in pressure drop only with respect to the velocity. If the water is moving really slow then 90's don't even matter.

Why am I saying this? Because if you aren't pushing the flow rate thru any particular pipe system then hassling with 45's will just be a waste of time.

You don't want to exceed 5FPS ever or you will have noise and wear problems. You reduce the velocity by using larger pipe since the same volume can get thru it at a much lower velocity.

http://www.shipcopumps.com/MathWizard/friction_sch40.html

So! If you are going to be pumping a lot of water thru a small pipe then either get sweep 90s or use two 45s.

Better would be to use spa-flex and a long gentle turn. These are far less resistance and much quieter. Spa-flex is good for overflow piping too as you can sweep them in a long turn down to sumps. This prevents falling and crashing water from your overflows.
 
Hello Kcress,
looking at the link that you supplied. if I am using a pump for my CL that is rated @ 2600gph, then 2600/60 min= 43.3. If I look on that chart, then 1in pvc would have a fps of about 15.755, in order to get to less than 5 fps it looks like I would need to use 2 in pvc. My next question would be:
if the pump has a 1 in output / input then I would need to use a 1in to 2in adapter, will I lose pressure/ velocity? I will be using this pump for a CL and I need the water movement for less chance of dead spots like I am currently having with power heads. Thanks for your schooling and time.
Robert
 
Hi Robert.

If you want maximum flow from your pump then you want 2 inch. If you don't care if you really only get something like 2000gph and maybe a little more noise go with the 1-1/2" as it will probably be OK as Amp suggests. Most would use it as it is a little easier to fit and plumb in.

As for adapters and the pipe size jumps. Yes you will lose velocity in the large pipe. But that's what you want! It will all be back at the nozzles in your display. You would actually keep your nozzle pressure because of the larger pipe.

Keep in mind the pressure drop numbers you see in that chart are for 100 foot lengths. It really isn't the straight stuff that we are concerned with for aquariums its the turns that cause all the reduction in flow at those high speeds.

If you run the 2 inch, the 90s, and the run lengths, will be completely inconsequential for any aquarium I can image.

If you run 1-1/2" then the elbows will actually represent a large reduction in flow at the resultant flow speed and you should hunt down 'sweeps' (much longer curves) or use spaflex if you can - or live with a reduced,(from otherwise available), flow.
 
Thanks again Kcress and Amphiprion. I appreciate the help. I held off doing this chore because I really only wanted to do this once. Now if I do use the 2 in to the tank would I be better off just letting the water flow out of the single 2 in or would I be better off dropping it down to several 1 in outlets?
 
You need to drop it back down as that is what increases the velocity. You should seriously consider Loc Lines as then you can point them where ever you want.

You can also ad eductors and multiply the flow many times. They would actually allow you to reduce the flow of your system (so you could use small pipe) and get the same or more flow in the display tank.

Here is an example of an eductor.
http://www.kthsales.com/website/vendors/Eductors/mixing_eductors.htm
http://www.toofishy.com/home.php?cat=743

Loc-line:
http://www.loc-line.com/products/index.html
 
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