Should I do a ¾” or 1” return?

eagle9252 · Feb 13, 2012

Need help deciding what size the return needs to be. Below is from the head loss calculator. I have about 300 gph on my 75 on ¾” now. I have 2 double power heads for the 120. I only have one of them in the 75 at the moment. I have not decided on the return size yet. I did buy a ¾” y and end pieces of the lock line to have two ¾” adjustable returns. I just don’t want all my flow in the DT coming from the return pump.
 
Specs for new return in the 120 DT
For ¾ return: 9.38 feet of head pressure, or 4.05 PSI. with a flow rate of 465 GPH.
For 1” return: 7.74 feet of head pressure, or 3.35 PSI. with a flow rate of 593 GPH

ripped tide · Feb 13, 2012

I feel like you might have your numbers backwards. 1" PVC has a larger holding volume than 3/4. If you build two identical returns, one out of 1" and the other 3/4, by the time both fill with water, the 1" will hold more water, have a heavier weight, and should have more back pressure than the 3/4". It also depends a lot on what the manufacturer reccomended for that size pump.

enderg60 · Feb 13, 2012

Your numbers are right, I would go with 1"

ripped tide · Feb 13, 2012

EnderG60;738248 wrote: Your numbers are right, I would go with 1"

Explain. Plz

I would assume that more water = more weight... More weight=more pressure so on and so forth.

eagle9252 · Feb 13, 2012

forgot to say what pump. it's a Mag 9.5 with 3/4 thrd. it will be ran as a single output until it reaches the middle of the tank and then at the exit it will wye out to 3/4 line lock and at the end it will go to a 1/2 flare tip thats 2 1/4 wide.

main question was should I stay with 3/4" or go to 1". as I dont think I need 600 gph going through the sump or should I?

Edit: 1" has more volume if you run the cal. all the fittings are the same and you only change the pipe size the head pressure will drop due to less friction.

thats why a house has 1" to the house and 3/4" main in the house and 1/2 to the fixtures and then you have 3/8 after most cutoffs at the sinks and toilets. 1" for volume and 3/8 for pressure

ripped tide · Feb 13, 2012

So the friction of a smaller diameter pipe is going to be the main reason or the slower flow rate?

Fwiw I use a 9.5 on my 93, with all 1" pipe. I have a manifold that feeds two reactors from the 9.5 and it is still reduced back before going into my tank.

My reAson for 1": doh! I thought that the extra water volume would slow the pump down... Apparently I was wrong

eagle9252 · Feb 13, 2012

why is it reduced back at the tank? is it because the drain can handle it or to slow down the flow in the sump? because at 120g x 5x turn over is 600pgh just asking

sree · Feb 13, 2012

eagle9252;738238 wrote: Need help deciding what size the return needs to be. Below is from the head loss calculator. I have about 300 gph on my 75 on ¾” now. I have 2 double power heads for the 120. I only have one of them in the 75 at the moment. I have not decided on the return size yet. I did buy a ¾” y and end pieces of the lock line to have two ¾” adjustable returns. I just don’t want all my flow in the DT coming from the return pump.
 
Specs for new return in the 120 DT
For ¾ return: 9.38 feet of head pressure, or 4.05 PSI. with a flow rate of 465 GPH.
For 1” return: 7.74 feet of head pressure, or 3.35 PSI. with a flow rate of 593 GPH

Returns are 3/4". The supply is 1". If you use the popular pumps like Eheim, the returns are only 3/4".

ripped tide · Feb 13, 2012

eagle9252;738272 wrote: why is it reduced back at the tank? is it because the drain can handle it or to slow down the flow in the sump? because at 120g x 5x turn over is 600pgh just asking

The drain can handle it, but at a slower flow rate it is not as noisy. The slow flow allows the water to filter more efficiently. I have a vortech in the DT for flow.

Edit: I'm probably putting 350-500gph through the display.

enderg60 · Feb 13, 2012

Ripped Tide;738254 wrote: Explain. Plz I would assume that more water = more weight... More weight=more pressure so on and so forth.

Pressure is a force over area. the only area you are worried about is the outlet of the pump. The force from the rest of the water is actually taken up by the reducer itself. Think of weight pushing on the sides of a funnel, which leaves you with the same overall pressure on the pump itself as a smaller pipe.

patrick · Feb 13, 2012

Actually, look up Poiseuille's Law....it relates to laminar flow. So for the same pressure applied to the water column.....the increased weight will certainly be a factor, but not as much as the radius of the pipe.......it factors in to the fourth power. It has the largest factor as a result.

Bigger is better....TWSS.....so go with the 1"....not WSS!

grouper therapy · Feb 13, 2012

The return can be 12"diameter and the flow will not decrease vs. 3/4" pipe. The larger diameter pipe 1" will have the higher flow. If the size of the body of water had a bearing on the flow a bottom closed loop would never work.

ripped tide · Feb 13, 2012

So you mean to tell me that if you set up a 9.5 pump plumbed directly into 12" diameter pipe that was 5' tall, you would get the same flow rate as if you hooked a 9.5 pump to a 1" diameter 5' pipe?

grouper therapy · Feb 13, 2012

Ripped Tide;738798 wrote: So you mean to tell me that if you set up a 9.5 pump plumbed directly into 12" diameter pipe that was 5' tall, you would get the same flow rate as if you hooked a 9.5 pump to a 1" diameter 5' pipe?

Nope I am telling you will get more in the 12" vs 1" with all other things equal. I already set up the 12" pipe +/- 60 " tall with a 1200 maxijet to prove it to LilRobb.

ripped tide · Feb 13, 2012

Interesting. I'm not trying to sound doubting, but I would love to see a video if you have one.

grouper therapy · Feb 13, 2012

Ripped Tide;738923 wrote: Interesting. I'm not trying to sound doubting, but I would love to see a video if you have one.

Don't have one . I'm not sure what good a video would do perhaps put to rest any question of my integrity you may have. A Maxi jet 1200 drilled in to the side of a 12" pvc pipe with water flowing out a hole in the top into a 5 gallon bucket is all would have seen.

Edit: You could always remove the return pipe out of the bulkhead of a tank and let the overflow represent a larger pipe and measure it yourself.

Edit: Throw a garden hose in the bottom of a swimming pool same thing.

ripped tide · Feb 13, 2012

I wasn't questioning your integrity, but in a large type scenario, I just think that the extra water volume and weight would effect the pump's abilities.

In a small water volume, i can see how the small weight difference would not 'out weigh' the the fact that larger pipes will create less friction.

grouper therapy · Feb 13, 2012

Ripped Tide;738934 wrote: I wasn't questioning your integrity, but in a large type scenario, I just think that the extra water volume and weight would effect the pump's abilities.

In a small water volume, i can see how the small weight difference would not 'out weigh' the the fact that larger pipes will create less friction.

It doesn't . The weight of the water on the impeller doesn't change. Based on your theory a diver in 60 feet of water in reservoir would experience greater pressure than a diver in 60 feet of water in swimming pool. Only if the depth/head changed is more pressure experienced.

. Water does not compress So the weight does not become any more concentrated.

Edit: There are other factors such as type of flow and turbulence that can affect the volume of water moved but .We assumed all thing equal besides pipe diameter.

lilrobb · Feb 13, 2012

I had the same discussion, and have it set to rest for a while...

There is a water test that I can't explain under the given equation below.

Water resistant clothing is categorized by it's resistance to water (measured in mm of water column):
http://www.abc-of-mountaineering.com/articles/jacketgearguide.asp">http://www.abc-of-mountaineering.com/articles/jacketgearguide.asp</a>

So with that being said, how does it fit the explanation that water weight doesn't change with varied diameters.

eagle9252 · Feb 13, 2012

mag 9 on 3/4" with 5' of rise

Total losses are 6.97 feet of head pressure, or 3.01 PSI. with a flow rate of 647 GPH. Process took 66 iterations.

mag 9 on 3" with 5' of rise

Total losses are 5.01 feet of head pressure, or 2.16 PSI. with a flow rate of 765 GPH. Process took 110 iterations

Should I do a ¾” or 1” return?

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