Looking for opinions on circulation schemes for a 400g tank

[M.E.Milz]

I posted this under the other thread I started titled "Large Pump Suggestions" (or something like that). So if you responded there, then obviously you don't need to respond here. It made sense to re-post this here under a different title because it was heading in a different direction.

The tank will be 78"x32"x36"tall (about 380g). I am trying to come up with a decent circulation system. Unfortunately, after talking to a number of manufacturers (Dolphin, Ocean Currents, SeaSwirl) and a few retailers and pump distributers, I am still confused as to the best arrangement. This is where I am so far.

I plan to use 2 separate circulation systems. System A is pretty well set, except for a final decsion on the pump. System B is still a problem.

Circulation system A:
2x 1.5" bulkhead drains in the tank (bottom of overflow) will be plumbed to my sump. 1x Ampmaster 3000 (or larger) pump will return the water from the sump and back to the tank via 8x 0.5" returns spaced along the rear wall of the tank at varying heights (ie, behind the rock work). Ampmaster sells a manifold that converts the 1.5" return line from the pump into 8x 0.75" lines. The 0.75" lines will be reduced to 0.5" just before entering the top of the tank (the splash gaurd along the rear edge of the tank is being drilled and fitted with 0.5" bulkheads every 6").

This system will have 6' of elevational head plus another 6' of head from frictional losses (assumption). The Ampmaster pumps about 1800 gph at 11' head (I need to double check this). Thus, I should end up with aroud 225 gph at each of the 8 returns. I may also go with Sequence pump having a larger flow rate for this system.

Circulation system B:
1x 1.5" bulkhead drain (also in the bottom of the overflow) will be connected directly to a second pump (ie, in a closed loop so as to by-pass the sump). This pump will then return the water back to the tank through either:
a) 2x 0.75" SeaSwirls, which can each handle 850 gph (the 1" models are too loud);
b) 3-4x Ocean Current Oscillators, which can each handle 500 gph; or
c) a motorized 3-way ball valve that will alternate the flow between return lines (straight plumbing) placed at each end of the tank.

Both a) and b) will require a large, high rpm pump becuase of the frictional losses of the oscilatting units. I don't think an Ampmaster 3000 will work because its flow is greatly reduce by back-pressure (as all low rpm pumps are). Thus, I would need a big, high rpm pump that will probably draw at least 4-5 amps. Another disadvantage is that the oscilators would probably need a lot of cleaning since they are being fed by intake connected directly to the tank. Between the 2, a) is probably a better choice because the SeaSwirls are designed for higher flow outputs.

c) is a good alterntive and more elegant solution than power heads on a wavemaker. But I have heard that motorized 3-way ball valves are fairly loud. The advantage is that I can use a much smaller pump (maybe my existing Iwaki 40RXLT) since the frictional losses will be much less.

Alternative Circulation system B:
Scrape the whole closed loop oscilator set-up and add 2-4 Gemini air-cooled powerheads (960 gph each) on a wavemaker. This would be the most enery efficient set-up, and the easiest to set up. The disadvantage is that the powerheads will be visible (although this might no be that bad since the top of the tank will be at 6').

Well, that is where I am at. I am open to any comments or suggestions on the above set-ups, as well as any other ideas.

Thanks for the help, Mike

 

[Cruiser]

M.E.Milz

A few considerations on your plumbing plans......

Circulation system A:
1. Will require a large sump water volume to feed the pump. Sump section where water is being drawn from.
2. The 6' elevation head you are measuring, is this to the top of the tank? or the top of the bulkhead fitting?
3. You will have more then 6 ft. of friction loss in your planned reduction from 1.5" to 0.5".
4. Can compensate by running 1.5" to the last possible section THEN reducing to 0.5"
5. Noise
6. salt-vapor leaving overflow box damaging surrounding walls.
7. Calculate your friction losses with planned plumbing pathways to determine which pump is needed.
8. 2.0" bulkhead fittings would have been better then 1.5"

Circulation B:
1. If the 1.5" bulkhead is located in the bottom of your overflow chamber, the closed loop will quickly become an "open loop", as it draws in air.
2. closed loops should draw water from the lower regions of the tank and return the water to the upper regions.
3. Closed loops (esp. SPS) should return water in the most turbulent / choatic pattern as possible.

How about numerous strategically positioned water jets boucning water off tank walls, rock work & each other to create the turbulent flows. This would allow the addition of whatever "seaswirls / oscillators" you want, as majority of the flow can be directed through the jets.

2 Ampmasters should be able to operate your system fairly adequately, and your could always increase the closed loop pump, or install 2 closed loop systems (3 - ampmaster / 1.1 amp pumps) if your REAL flow happy!

Just a couple of thoughts while lurking through your post.

 

[npaden]

I just set up my 415 with your option A & B and I was way short on circulation. I'm now messing around with different options to get what I need.

I would say you need 2 Ampmasters on recirc loops and 1 as a return. Another option for a return would be a sequence. They use a little more electricity than the ampmaster but IME are more dependable and they have several different options for gph from 3,000 gph to 5,000 gph.

Another thought for your recirc loops would be that I would recommend a minimum of 2" intakes or you will be sucking snails through the strainer screen. I had 1 - 1.5" intake for my recirc loop and it had so much suction power it was sucking air from the top of the water and it was set 5" below the water.

Just a few quick thoughts. Recirc loops are the best way to get water flow on big tanks imo.

FWIW, Nathan

 

[npaden]

Another thing you need to keep in mind is water velocity. You want to maximize flow but minimize velocity.

The .5" return will have tremendous velocity - enough to rip tissue off a coral directly in their path. You would be better off to incorporate at least 1" returns and the best option would be 1.5" returns if you could drill them without having the big pipe sticking in the tank.

FWIW, Nathan

 

[M.E.Milz]

Thanks for the replies. I have narrowed the options down a little.

With respect to circualtion system A:

This is essentially is the return from my sump, and I am shooting for 3000 gph total flow. If I run any more than that, then I probably won't be able to use the sump (32"x 24") as a refugium.

Although my original description may not have been that clear, the 1.5" return from the pump will feed into a manifold having a total of 8x 3/4" lines. The manifold will be placed near the top of the tank. From the manifold, each of the 3/4" lines will be connected to a short (1'-2') piece of 1/2" tubing, which will only be used to extend the return down into the tank behind the rockwork.

I don't expect the back pressure to be that great from the manifold since the cross-section area of the 8x 3/4" lines is almost twice that of the 1.5" return. However, I do expect some back pressure when reducing each of the 3/4" lines down to 1/2". If this turns out to be too large, then I could always replace the 1/2" pipes with something larger. Anyways, this is how I came up with a guesstimated total head of 10'-12'.

As I explained above, I am shooting for 3000 gph total through these 8x return lines. That means each return will carry 375 gph, which should not have that great of a velocity even if coming from a 1/2" line (less than a Rio 800).

The key is to find an efficient, quiet pump that will deliver the 3000 gph through this plumbing system. I don't think the Ampmaster 3000 will do this. At 10'-12' of head, the flow rate really drops.

With respect to circulation system B:

Option B is out. I just don't think the Ocean Current devices are desinged for high flow, large tank set ups

Option C is out. The motorized 3-way ball valves are too expensive and noisy (at least that is what I have heard).

Option A appears to be the best choice. But I am inclined to go with 2x 1" SeaSwirls, one placed at each of the front corners of the tank. If I drive 800-1000 gph through each of these, then I should be able to create plenty of turbulence in the tank, particularly if I neck the outputs down a little to increase the velocity.

Now, all I have to do is find a pump that will drive both SeaSwirls at this flow rate. I know that the Iwaki MD100 will do this because it can handle a lot of back pressure without a big loss in the flow rate. I am not so sure about the Ampmaster 3000, since this pump is sensitive to back pressure. By the way, I will have two Iwaki 40RXLT pumps left over. Although these pumps are not that great for pressure applications, they might work out if I use one pump for each SeaSwirl.

General considerations & comments.

I am checking to see if I can increase the size of my drain bulkheads to 2" each. Otherwise, I will go with 4x 1.5" bulkheads. Either way, then that should take care of any flow related issues.

Questions:

Nathan, it sounds like you are suggesting that I reverse my circulation schemes. If I follow you correctly, perhaps I should use the return from my sump to drive the pair of SeaSwirls. And use the closed loop for my multiple tank returns (the 8x 1/2" lines behind the rockwork). If I do this, then an Ampmaster 3000 should work becuase I have eliminated the 6' of elevational head. The Iwaki MD100 (or pair of 40's) would also probably work for the SeaSwirls, even though these will now have an additional 6' of elevational head. I will have to give this some more thought.

I have another question on the location of the inlet for my closed loops. Right now, I plan to have the inlet in the bottom of the tank in the overflow chamber. To keep this drain/inlet from running dry, I plan to use standpipes on the other drains that feed the sump. Thus, the water in the overflow chamber should remain near the top of the tank, and the inlet that feeds the closed loop will be at least 30" below the overflow water level.

The advantage to this is that I avoid bulkheads in the back of the tank, and I avoid snails/fish from getting sucked against the inlet. The drawback is that all of the water flowing through both circualtion systems must flow into the overflow chamber. Any comments??

Thanks again for the help.

 

[M.E.Milz]

Ignore most of the above. I have a new plan (and I will keep this brief).

3 separate circulation systems:

System A:
2x 1.5" drains feeding into sump. 1 AmpMaster 3000 (or larger pump) returning water through 8x returns spaced along back wall of tank and mid-height.

System B:
1x 1.5" drain connected in a closed loop to an Iwaki 40RXLT pump and returned through 2x 3/4" SeaSwirls at the front corners of the tank.

System C:
1x 1.5" drain connected in a closed loop to an Iwaki 40RXLT pump and returned through a 1" 3-way motorized ball valve, which alternates flow between 2x returns at opposite ends of the tank.

That should give me 4000-5000 gph total turn-over, and plenty of random movement.

 

[npaden]

M.E.,

I guess I should have asked on what you are planning on keeping in the tank, but if you are thinking SPS you are going to be significantly short on water flow.

As far as velocity goes, a 1/2" diameter pipe has an area of .2 sq. in. at a flow rate of 375 gph this is a velocity of 123 in/s. 375 X 8 = 3,000 gph. Lets say we split that same flow 4 ways instead of 8 and use 1" pipe instead of .5" pipe. The 1" pipe has an area of .79 sq. in. at a flow rate of 750 gph - this results in less than 1/2 the velocity - 61 in/s! Again - the key ingredient in water flow is high flow with low velocity. The 4 1" returns would be a MUCH better option.

Another thing is that you are assuming 375 gph through the .5" pipe on this, but one thing you may not be calculating in completely is the tremendous friction loss (back pressure) resulting from narrowing down the water flow to that small of a diameter pipe. There are some calulators on that if you need to see them but trust me, the smaller the pipe the more friction loss. The larger diameter pipe you can use the better in nearly every situation.

The problem with using drains for recirc loops would be the fact that you will be creating turbulence by the water flowing over the top of the overflow and you have a good chance of creating and then sucking a bunch of bubbles into the intake of your recirculation loop. The benefit to drawing the intake from the back wall of the tank is really two fold. First there are no bubbles, and 2nd - you really add to your overall water flow as you are sucking in water to the intake as well as pushing water out of your output. Careful planning in the placement of the intakes can eliminate stagnant areas behind the rockwork.

On the intake if you make it large enough you don't have to worry about sucking in snails or fish. A 2" intake would give you an area of 3.14" and at a flow rate of 3,000 gph your velocity is at 61 in/s. In my experience this is low enough suction that using a standard bulkhead strainer screen a snail can crawl across the strainer unharmed.

I really would think hard about recirc loops. Large diameter plumbing as well. I would say 1,500 gph would be all you needed in the drains and return from the sump with 6,000 on 2 recirc loops with ampmasters. That would give you good water flow IMO.

FWIW, Nathan

 

[Cruiser]

M.E.Miltz & Nathan

"Nathan" has some really good points regarding plumbing set-up, especially regarding flow / velocity. Its much hard to get large flows with low velocity then the other way.

Nathan, I think your calculations are on the slow side for velocity.....

Velocity calculations ->excluding friction lossesfor 1/2" pipe follows: (assume 1/2" is 0.5" - ID is less)
0.7854 x D(squared) => 0.7854 x 0.25 = 0.20 (0.19)
0.20 x 12" piece of 1/2" pipe = 0.20 x 12 = 2.356
2.356 divided by 231 = 0.0102 cubic inches or gallon.
So in a 1/2" pipe, 1 foot long there is 0.0102 of a gallon.
Ampmaster 3000 gph => divided by 60 minutes, divide by 60 seconds = 0.8333 gallons per secNow divide 0.0102 by 0.8333 will result in
the velocity in feet / sec = 81.69
Multiply by 12 to get inches / sec = 980.28

So 1 foot of 1/2" pipe produces a velocity of 980.28 inches / sec -> EXCLUDING friction losses.
You won't see this flow from the ampmaster through the 1/2"!

Even with your 40RXLT, you should calculate flow / friction losses to optimize the pumps abilities.

In addition to what "Nathan" mentions regarding the recir. loop pump suction side located in the overflow box, this pump will "suck" dry the overflow chamber "buffer" you create with standpipes.

You should not have any issues regarding sucking in a snail or damaging a snail if you use 2-1.5" bulkheads, i.e at each corner on back pane or 1-2.0" or 2-2.0". There are numerous types of "bulkhead screens" available & you can make your own from PVC.

Nathan love that TANK!
Hope this helps.....

 

[M.E.Milz]

Thanks for the input guys. I will have to experiment with using 8x 1/2" returns vs. 8x 3/4" returns. As Nathan points out, I want volumn, not velocity for these returns (particularly since they will be directed out through the reef structure).

I will have to think about moving the recirculation inlets from the inlet box to the back wall of the tank. This does present the problems because the tank must sit fairly close to wall. I am also concerned about installing a bulkhead in a location that cannot be reached without tearing the reef down. Anyways, I will have to give this a closer look.

By the way, I will keeping mostly sps. But you might be surprised as to how well the sps colonies are doing in my current 200g with very little turn-over and no wave-makers. I am currently only using the 2x Iwaki 40RXLT's as return pumps and 2x power heads (and the Iwaki's are turned down because the overflows cannot handle them at full output). But of course, and as Nathan pointed out, it is better to have too much flow than not enough.

Thanks again, Mike

 

[Cruiser]

M.E.Miltz

Anytime.

I remember seeing pictures of your 200 gallon tank, which was very, very, very nice. SInce doing this for a longtime, I really liked your healthy watanabei(sp?) angels.

Good luck with the new set-up

 

[M.E.Milz]

Thanks. By the way, the male & female wantanabe (sp?) angles are still doing fine.

 

[SPC]

Posted by Mike:
This does present the problems because the tank must sit fairly close to wall. I am also concerned about installing a bulkhead in a location that cannot be reached without tearing the reef down.

Mike my tank is drilled in the back with 1 1/2" and 6" is the clearance I needed from the wall, actually that gives me 1" of play against the wall.
I am not quite sure what you meant by having to tear the reef down to reach the bulkheads.
Steve

 

[M.E.Milz]

This tank is going into the living room of our new condo, and I am under strict instructions (from the spouse) to make this thing look like it is built into the wall. I can't do this if it is sitting more than 3" or so away.

As far as the access issue, the bulkheads will undoubtedly be behind my rockwork, which will up the back of the wall. I won't be able to get to the bulkhead to clean or repair the strainer if that should be necessary.

 

[npaden]

Cruiser,

I'm actually using a spreadsheet to calculate the flow rates. The calculation is figuring the velocity of the water exiting the outlet and doesn't factor in how far the water travels. (I'm confused why you are figuring in the 12" length of the 1/2" pipe) I got the spreadsheet from a friend but here is the calculation. To be honest I don't understand the equation but I think it is right. Assume the flow rate is A (in gph) and the Area of the pipe is B (in cubic inches).

AX(3785/3600)/((3.14X((BX2.54)^2)/4)

Heh!

See if that makes sense to anyone else!

M.E.,

You might check out my plumbing page for some input on the closed loop with coming through the overflow box. Check out the left overflow. I would do this again using 2" intakes coming up on each side and having a bulkhead on the side of the overflow box.

www.padens.homestead.com and click on the plumbing link. I would make several changes from this (Mainly adding another recirc loop on the right side) but you get the idea.

BTW, My tank is 2" from the back wall.

FWIW, Nathan

[ January 25, 2002: Message edited by: npaden ]</p>

 

[Cruiser]

Nathan

AX(3785/3600)/((3.14X((BX2.54)^2)/4)

Thats quite a complicated formula thats fairly confusing

.

Generally:
A = Area
Q = Flow
Area = square inches
Volume = cubic inches
Velocity = feet / sec

I see part of the formula -> 3.14(pi) x (B x 2.54 to convert to centimeters)^2, then divided by 4???
Also 3785 should equate to 3.785 liters per gallon, then the rest of it I'm totally lost

.

Area equals -> PI (3.14...)x Radius^2 or 0.7854 x diameter^2.

I used the additional 12" or 1 ft to convert the area to volume (could of used 1" section for calculations, but 1 foot is easiest). The volume divided by 231 (cubic inches / gallon) to get the volume of a 1 foot section of 1/2" pipe. Divide this by gallons per sec of the pump, and you get velocity of feet / sec, and then convert to inches per sec.

I assume your formula produced cm / sec?
Your flow chart might already have taken into account friction losses or equivalent head loss / 1,000 ft of pipe.

Joe

 

[Russ1]

Check out the Jacuzzi pumps. 2inch in 2 inch out and can pump as high as you need just increase the hp! Pretty quiet for a large pump! Russ

 

[Wrasse]

Nathan, now I understand how you have your tank plumbed. Extending the drains for the closed loops up through the bottom and then out through the side of the overflow chambers was a pretty slick idea. I will have to give that some thought. But I am running out of time, so I will have to make a decision pretty quick. Mitch at Inter-American (where you got your tank, right?) plans to start building my tank within the next week or so.

By the way, how do you like the 1" Sea Swirls? I have been told that they are louder than the 3/4" units. Is that really the case?

MEMilz

 

[npaden]

Milz,

For the intakes for the closed loops I would go with 2" bulkheads and for the drains I would use 1.5" bulkheads - you will actually want to flow more through the recircs than through your drains. Also I would set it up with a recirc loop on each side of the tank. You will have to figure out where to add the return from the sump though, you may end up with 4 holes in one overflow.

Another thing would be to put the intakes a little farther down from the top of the water line than I did. I would go at least 8" center on the 2" intakes for the recirc loops.

Originally I whined about the noise on the 1" sea swirls, but I haven't been able to get my tank quiet enough to hear them with everything running yet!

Yes, I got my tank at IA from Mitch. Tell him Hi for me.

Later, Nathan

[ January 25, 2002: Message edited by: npaden ]</p>