return line size ?

[blackaero1]

I finally got my sump yesterday and will start plumbing it today hopefully once I get all the stuff I need. However, I have heard 2 schools of thought on the return line. I'll start with tank specs to give a base to go from. 75g AG tank, will use a hob overflow until I can get the tank drilled and a calfo setup built for it. The sump is 30x16x16 with a 10" section for the skimmer and a 8" section for the fuge, both dump into the center where the return will be. I have a mag drive 9.5 pump for the return (although I have been told this may be a bit large for me). The pump has a 3/4" outlet on it.
Heres what I've heard:
1) upsize the return line to 2 times the outlet size on the pump for max efficiency and quiet operation- this makes sense to me as this pump moves a ton of water.
2) keep the return line the same size as the outlet as it will only be as good as its smallest point. I understand the theory on this one, but it still seems like #1 is the correct way.
Now I only have about 4 ft of head pressure to worry about so I'm looking at around 800gph from the return, my overflow can only handle 600-700 gph (single 1" drain). I am considering putting a branch in the return to send some of it back into the fuge area, thus slowing down the return into the tank. I am also more than likely going to split the return so I have an outlet in each back corner of the tank, this should eliminate some of the flow as well with the addition of a a few more fittings in the pipe. If this proves to be way to much for a efficient sump system I may just replace the 9.5 with a 7 as it will obviously slow down the flow (I think it would be around 480gph if I remember right).

 

[buckster71]

Also, make sure you have a shut off valve on your pump outlet. You can also use this to:
1)shut off water returning from the tank to the sump for maintenance
2) ability to adjust your outlet flow from the pump.
I would go with the same size pipe as you will also create a pressure drop in the return by adding bigger pipe.
I'm wondering if this will also add cavitation and air pockets as the pump is actually designed to flow into a 3/4" pipe.
I think you may have it confused with enlarging the inlet?
I have a 72 bow (actually two of them now) and I run MAG 7's with 1/2" return and my flow is fine. I probably have the same head pressure of 4' too.

 

[blackaero1]

I got the pump used from someone else and he said that when he got it a few months ago, the manual stated to use pipe 2 times the size of the outlet for max efficiency. I've talked to some reefers in the area and they tell me it will quiet the system down if I can upsize, then at the last minute reduce back to something smaller to increase the pressure at the outlet. I ended up going with 1 1/4" pipe for the return and its sized down to 1" for the outputs in the tank. I also have it set up so I have a branch into the fuge area with a ball valve to control the flow more precisely. This way, the pump doesn't get slowed down except for head pressure and all the joints in the line. After its complete I'll make sure to post how it works and if I need to rework the whole system or not. I have plenty of valves to turn stuff off for maintenance or regulate certain areas for flow as well as unions so I can take it apart easily if I ever need to for maintenance.

 

[buckster71]

Make sense. When I redo my piping on mine, I'm going from 1/2 to 3/4, because I wanted to minimise the pressure drop to the tank as I am running a ((properly sized pump)) instead of an oversized one.
What you are talking about is the Venturi effect based off of Bernoulli's equation
http://en.wikipedia.org/wiki/Venturi_effect

It will also apply to all of your valves as well. After every smaller oriface you are going to get a pressure drop, which is going to work against you in dealing with head pressure.
Going from a smaller outlet to a bigger pipe is going to create pressure drop. Also with each of your fittings. Probably if you have some of 90 degree fittings you'll be a.o.k with larger pump. If you are worried about velocity of the water at the outlet, place one of those wide outlets on it. This will slow down the flow over a wider area, but not decrease it.

 

[donald]

I run a quiet1 4000 pump as the return from my fuge. It came equiped with 3/4 fittings and I went up to 1 in. Where it comes into the tank I have it go into a lockline "y" 3/4 size and I have 3/4 to 1/2in reducers on the ends. A small sugestion on pump size, when in doubt go bigger, you can always throttle it back with a ball valve but if the pump is too small it's a real headache!!!!!!!!!!!

 

[ameno]

going up to 2x dia. on your return will increase your flow rate, I think that is the normal recommedation on most pumps,and the flow rate that is given for the pump is based on this. the larger size reduces friction loss.
since your pump is capable of higher volume then your drain going the same size will probably pull the gph down to close to what your drain is providing.
I would also suggest putting in a union at the pump discharge for easy removal of the pump. I go up a size on my unions because the inside dia. is smaller then your inside pipe dia.

 

[buckster71]

All right, All right.
Just to clear up the confusion I found this page to discribe waht I'm talking about. Pay attention to #3 on the web page. The pump is going to put out it's designed flow at 60 HZ, which is 100% power supplied to the pump. If the flow is 900 gph, you get 900 gph regardless from teh pump outlet. Head pressure is what is going to get you. Now he is oversizing his pump. And actually, fluid dynamics is pretty self explanitory in the next paragraph. Now with each orifice dimension change you are going to create more pressure drops. Pressure is what is needed to overcome gravity at this point. Like it best to remove the 90's and use flexible hose bends if flow becomes a problem.
http://www.****
Please do not post links to other sites
3. Matching pipe diameter to your pump output nozzle is important so that flow is not restricted ie 1" pipe to 1" output nozzle. Equally, too wider pipe may restrict flow when pumping upwards, due to the increasing weight of water held in the pipe in comparison to the output pressure of the pump itself. If increases in diameter are called for, they should only be small increases. (See diagram below) A&B. The volume of water in pipe 'A' will be significantly heavier than he weight of water in pipe 'B'. To this end, Pipe 'A' will have a more serious effect on pump output per vertical meter than pipe 'B' due to increased back pressure, especially if your pump only has a 1" outlet nozzle. In pipes 'C' & 'D' the opposite applies, i.e. pipe 'C' will be more efficient and less restrictive for the pump than pipe 'D' as there is no weight involved when pumping horizontally, however velocity will be lost. Pipe 'D' will be more restrictive due to its smaller diameter however velocity will be increased.
Earlier posts had some reefers stating that pumps worked less with double pipe diameter changes, but it has realatively nothing to do with flow, but pressure or velocity.

 

[cannarella]

I disagree to an extent. If your sump it under the and you have to push 5ft of head then matching the outlet is not going to hurt you.
If you are pushing 15ft vertical and 20ft horizontal, like my tank, then you really need to look at the static loss of the pipe size. Go punch in some number into the head loss calc over on -- . I put in some specs of a Iwaki 40 RT-2 pump with a 3/4" inlet and outlet on the specs of my plumbing with 3/4" line. The result was:
Total losses are 18.17 feet of head pressure, or 7.85 PSI. with a flow rate of 353 GPH
1" line:
Total losses are 16.58 feet of head pressure, or 7.17 PSI. with a flow rate of 449 GPH
1.5" line:
Total losses are 15.29 feet of head pressure, or 6.61 PSI. with a flow rate of 512 GPH
Minimal PSI loss but 150 GPH gained.
Think of it this way would you rather breath through a coffee stirring stick or through a McDonald's straw?
Right now I am setting up my system and I have water flowing. It is being driven by a GenX PCX30 temporarily. The manufacturers specs says it's max head is 14.5'. I am running it at over 15 ft of head and it pushes about 100 GPH at that height on 1.5" line with lots of twists and turns. I can't imagine what the Sequence 4300 will push through it.
If you are going between floors or over a long distance up size, if it is just under the tank then keep it the same size. These are my opinions from testing and research. I am by no means a fluid engineer, but I did stay at a Holiday Inn Express last night... HTH

 

[buckster71]

"Think of it this way would you rather breath through a coffee stirring stick or through a McDonald's straw?" I believe the bigger difference in this analogy is that air is compressible and water is not.
In reality the changes are in reality minute. My whole thing was explaining that if you go from a smaller diameter to a larger diameter you create a pressure drop, which in fact will decrease velocity and pressure and may in turn change your head pressure rating. As a Mag 7 would go from 1/2" to double size 1" pipe, that it is quite a change. Flow curves are probably based upon using the same pipe diameters as the outlet themselves. I was suggesting to the orginal poster that going up too much may not give him entirely what he wants. There was another page I found that has some more ideas to think about.
http://www.****
Please do not post links to other sites
This in reality is kind of getting blown out of proportion. Also, the friction factor in dealing with these equations are usually dealing long pipe lengths, as stated above
However, I did some experimentation on that -- page and noticed that if I added 2 ball valves and 2 90 degrees it didn't change the flow ratings that make abosutley no sense as it should increase your head pressure losses and change your flow. This page seems to put more emphasis on the major restrictions of the pipe, than the minor restrictions of the bends and twists...which I'm not sure is entirely correct.
Now since I don't have all the variables to plug into the equations on this page:
http://www.******
Please do not post links to other sites
I'll leave it alone

 

[cannarella]

I may not have specified at the other end you neck it down to the origonal size. My bad. I totally agree that if you discharged out of a pump with a 3/4" fitting and went to 1.5" and it discharged at 1.5" you would have pressure drop.
Let me ask you this, say you come out of a pump at 3/4" and then ukp it to say 1.5" and at the discharge area nock it back down to 3/4". How would that affect it?
In other discussions I have had, which suppot my line of thinking, my gut just tells me that increasing the diameter between the pump outlet and discharge will reduce friction therefor increase flow (gph) rate with little to no affect on pressure.
I smell an experiment coming on...

 

[ameno]

The manual for my mag pump recomends 2X on pipe dia. for max. flow rate.
I can understand your logic that the weight will be greater because of more volume, but this is a much smaller factor for head loss then what the friction factor on a smaller pipe dia will bring, to have a smaller section with a smaller dia. pipe will not cause much friction loss as would a longer area. I've been a piping engineer for over 20 years for major industries so I know a little about this stuff. Every system we install goes up in size on the pump discharge, some valves will cause restriction and some don't, a ball valve that is a full port valve will not. Here is an example based on design from Cameron Hydraulic data, a 3/4" pipe flowing 900 gph will have a velocity of 9.025 fps. and a head loss of 18.8ft per 100ft. when the line is increased to a 1.5" dia. the velocity is 2.36 fps with a head loss of 1.7 ft per 100 ft. So as you can see there is a major difference in head loss between the two pipe sizes.
another thing that is sometimes misunderstood is pressure, the amount of pressure that a pump produces is not increased when the line gets smaller, it's the velocity is what increases.

 

[cannarella]

If you calculate the pipe internal diameters and flow rate you will see even though the flow decreased when the pipe size increased it is still moving the same amount of fluid. Just the head has changed. So with the lager diamater you can add more twists and turns with little affect on the head pressure compared to a smaller diameter pipe. Would you say that is correct Ameno?

 

[ameno]

yes thats correct, the velocity will change, when the flow maxes out on the velocity in can flow at then the volume will decrease. then with adding other restrictions such as elbows the smaller line really slows down the flow rate.
A good example is if you have a valve in the line and you start closing it, say your flowing 900 gph, when the valve is half closed it's flowing more then 450 gph just a higher velisity, the flow decreases as the velosity increases.

 

[buckster71]

Good points.
I've been enjoying the research!
Let's just not start into laminer and turbulent flow discussions

Through it all now I realize that I have to upsize my pump to add features to my tank (ie, chiller and UV sterilizer), as I have to add some more pipe for these items.
I agree on upsizing the pipe, but generally wondered the benefit of double sizing, besides less heat due to friction and heat (work) by the pump, especially in this type of setup.
If you are worried about the flow coming out at the end of your return, they do sell spreaders (wide outlets) that really will knock down the velocity in your tank.

 

[ameno]

I think the pump manufacture recommends 2X in order to get the max. amount of flow there pump can produce, but not really something you have to do, on my return I went from 3/4" to 1" on the return, 1" gives me around 900 gph, if I had gone to 1.5" I could get around 1050gph. Since I was only going up less then 4ft it only reduced flow by 150 gph, I was willing to sacrifice some flow in order to use a smaller line. So it just all depends on how much flow you need.
Oh come on lets get into some laminer and turbulent flow discussions

Just kidding, like to keep things simple

 

[blackaero1]

Update: Went with a 1" drain (kept it the same out of the overflow) with a mini durso inside the hob overflow. For the return I went with 1 1/4" coming off my 9.5 mag drive with a 3/4" outlet. I also have the return branched off back to the fuge with a ball valve to control water flow into the tank. This thing moves A TON of water. Unfortunately I think I may have gone too large for the return pump. Even with the water going into the fuge, so much that it would keep me awake at night if I tried sleeping in the same room, the pump is still pumping more water into the tank than its draining. I'll try to tweak it better but its working for now as I only lose about 1/8" in my sump over a 24 hour period. I have the return split so it returns at teh back coners and both of those are drilled for a siphon break in case of power failure. So now my two options are 1) change the pump to a mag 7- this is probably the easiest way to fix the problem or 2) get a second identical hob overflow so I can just add a drain to the tank. This would work wonderfully to provide better surface skimming buit finding an identical overflow has proven harder than I thought as I bought it used from a friend and so far I can't find the same one anywhere online. If I change the pump I could then use the 9.5 as a dedicaterd mixing pump.

 

[buckster71]

The moral of hte story....
Don't buy used crap....lol
This has been a good post.
PS. what was so noisy? Maybe you just need to put a pad under the pump to cut down the noise? Vibration? To much water running noise?
You might also be able to put the fuge pipe underwater this will cut down the trickle noise?
PS. If you throttle it back say about 50%, then you are too oversized. Plus the resistance might even start to create heat. Actually, my Mag 7 through my sump on a 72 bow still out-preforms the overflow if it is wide open. I have to run my sump way above the level mark to keep it from sucking air. I did get over excited and slapped it together without much afterthought and research.

 

[blackaero1]

The part that is noisy is the extreme amount of water rushing out of the fuge. The pump is dang near silent, when I was able to get the fuge overflow silent the only sound I heard was the water coming out of my skimmer and that was quiet in comparison to the rush of water I currently am hearing. Although, when I have the fuge overflow silenced the return empties its section of water in about 30-40 seconds easy. The sound is directly impacted by the amount of water I have going to the fuge from the return pump. If I cut it off and only have the drain going a full throttle, I hear nothing. Its only when I divert the return into it. I ended up getting a new overflow box today with 2 1" drains (advertised as a 1000gph). I would have preferred a second box identical to the first so I could have one on each half of the tank but it just wasn't doable as I couldn't find an identical one no matter how hard I looked. The sad thing is, the new overflow is a bit larger (which is really a good thing), but it is so much larger that I will now have to remove and change all my plumbing. Drain for obvious reasons, return because I have it split so it goes to the back corners of the tank. The pipe that goes from one side to the other is about and inch, inch and a half too high for the new overflow to sit properly on the tank. It will be a simple matter of adding some pipe to places and removing from others, but it still sucks. Looks like another trip to home depot and more money spent.

 

[buckster71]

AH YES
Trips to home depot.
electrical -- check
plumbing -- check
second

[hr]
-- check