Calling all math geeks

[Strawberry]

I am currently designing a custom tank build and I have a simple question that requires a good bit of background to explain.
I am aiming for a turnover rate of 30-40 for a 75gal frag tank that I plan to make as my display.

Dimensions: LxWxH 38”x38”x12”

I am going to drill holes in the center of the bottom panel for a true bean-animal overflow tower in the center. (Some call it a tower overflow or a center overflow, but it is basically a square weir in the center)

I want to make this overflow as small as possible so that it does not distract from my display, while leaving enough room to install 3 bulkheads for the bean animal design.

Essentially, I used the inner diameter value of schedule 80 PVC for the following nominal pipe sizes: 3/4”, 1”, 1 1/4”, 1 1/2”, and 2”.

The formula I used to calculate flow rate:
V= CdA(2gh)^.5
where Cd was calculated using (Cc-Cv)
Cc as contraction coefficient over a sharp edge aperture (straight edge) (.62)
Cv as the velocity Coefficient of water (0.97)

These calculations are much easier to do using metric values, so I converted all of the PVC pipe ID square inch areas into square meters.

The result of volumetric flow for a single aperture of each nominal pipe size are as follows, considering I used 11” as my height value (because I want my display tank filled to 1” below the rim)

3/4”= 148.9 gal/h
1”= 241.2 gal/h
1 1/4”= 419.76 gal/h
1 1/2”= 787.32 gal/h
2”= 939.2 gal/h

FINALLY, my question. I am not really sure how the bean animal piping is setup; I know that 1 of them should have a full siphon, so I can assume the full amount of my calculated volumetric flow rate. One pipe must have a partial siphon, right? And the last is an unused emergency drain, right? If anyone can relate my rambling to the bean animal drain setup and explain how much flow rate I can assume from the pipes that are only partially siphoned, I’d really appreciate it.

Thanks for reading this, even if you aren’t a math geek! I have put a lot of time into this because it’s still a ways out of reach, but it’s my dream build and I want to make sure it’s perfect. Happy reefing!

 

[Strawberry]

Bump

 

[sharpimage]

I would go with 1" bulkheads and add power heads for flow. Larger bulkheads are going to take alot of real estate up

 

[JoshH]

So what you are trying to achieve here is actually a modified Bean Animal drain design. I agree going with 1" will work well, a 1" pipe at full siphon will flow around 900GPH which is over 10 times your display volume. If you're looking to have all your flow coming from your return it's probably going to limit your coral stocking as you won't be able to provide varied flow that so many corals like. You could up your plumbing size to 1.5"-2" and achieve the numbers you want but those bulkheads are MASSIVE and would make your overflow atleast 10" x 10".

Is there a particular reason why you want to go with Schedule 80 pipe? You will get more flow from schedule 40 or even schedule 20 and theres no need for the thicker schedule 80 in our hobby with the flow rates and pressures we work with.

A Bean Animal drain has one full siphon drain that you adjust via a gate valve until just a slight trickle flows down your secondary line (not even a partial siphon) and then a third emergency drain. I might consider a Herbie drain setup as it is basically the same thing minus the third emergency line. You still have the safety factor but it will take up MUCH less space and give you the ability to have a smaller overflow

 

[Miller535]

So what you are trying to achieve here is actually a modified Bean Animal drain design. I agree going with 1" will work will, a 1" pipe at full siphon will flow around 900GPH which is over 10 times your display volume. If you're looking to have all your flow coming from your return it's probably going to limit your coral stocking as you won't be able to provide varied flow that so many corals like. You could up your plumbing size to 1.5"-2" and achieve the numbers you want but those bulkheads are MASSIVE and would make your overflow atleast 10" x 10".

A Bean Animal drain has one full siphon drain that you adjust via a gate valve until just a slight trickle flows down your secondary line (not even a partial siphon) and then a third emergency drain. I might consider a Herbie drain setup as it is basically the same thing minus the third emergency line. You still have the safety factor but it will take up MUCH less space and give you the ability to have a smaller overflow

I agree with this. Your flow should NOT all come from your return pump. The better portion should come from power heads. On top of the issues with flow for corals as stated, too much flow through a sump does not allow enough contact time for filtration in the sump, like skimmer and reactors.

 

[Silent]

Your flow numbers seem way off.

 

[Strawberry]

I thought that the turnover rate in the tank was only considering the tank return and cycle from sump to display. I get kind of mixed up considering the difference between recommended flow rate and turnover rate. I do plan on having powerheads for random flow patterns.

 

[Strawberry]

Your flow numbers seem way off.

How should I correct this? I can show how I worked this out, maybe I skipped a step or messed up on a conversion.

 

[JoshH]

I thought that the turnover rate in the tank was only considering the tank return and cycle from sump to display. I get kind of mixed up considering the difference between recommended flow rate and turnover rate. I do plan on having powerheads for random flow patterns.

Reccomend tank turnover is flow from powerheads and your return combined. Sump turnover is how often your system volume is run through your sump. Typically the reccomended sump turn over is 3-5 times your system volume unless you plan on running a specific filtration setup like the Triton method which calls for 10 times turnover.

 

[Miller535]

Reccomend tank turnover is flow from powerheads and your return combined. Sump turnover is how often your system volume is run through your sump. Typically the reccomended sump turn over is 3-5 times your system volume unless you plan on running a specific filtration setup like the Triton method which calls for 10 times turnover.

Yep

 

[Strawberry]

I agree with this. Your flow should NOT all come from your return pump. The better portion should come from power heads. On top of the issues with flow for corals as stated, too much flow through a sump does not allow enough contact time for filtration in the sump, like skimmer and reactors.

The flow rate is just an estimate of how much water is escaping the tank through a hole that size each hour, gravity fed. I don’t mean to base my desired total flow off only the return pump cycle. I wanted to use that estimate to make sure that the pipe was the right size for my return pump, and I think it is recommended for a tank this size to have 6 turn overs each hour. But I’m not 100% sure.

 

[Strawberry]

So what you are trying to achieve here is actually a modified Bean Animal drain design. I agree going with 1" will work well, a 1" pipe at full siphon will flow around 900GPH which is over 10 times your display volume. If you're looking to have all your flow coming from your return it's probably going to limit your coral stocking as you won't be able to provide varied flow that so many corals like. You could up your plumbing size to 1.5"-2" and achieve the numbers you want but those bulkheads are MASSIVE and would make your overflow atleast 10" x 10".

Is there a particular reason why you want to go with Schedule 80 pipe? You will get more flow from schedule 40 or even schedule 20 and theres no need for the thicker schedule 80 in our hobby with the flow rates and pressures we work with.

A Bean Animal drain has one full siphon drain that you adjust via a gate valve until just a slight trickle flows down your secondary line (not even a partial siphon) and then a third emergency drain. I might consider a Herbie drain setup as it is basically the same thing minus the third emergency line. You still have the safety factor but it will take up MUCH less space and give you the ability to have a smaller overflow

I’m trying to go with the smallest size possible, maybe just over thinking it a little. Because I have plenty of time to design it, I just want to make sure it’s correct. I guess that I could use schedule 40, but I thought it was only rated for drain pressure? I’m still learning a lot of these things, so please be patient with me lol

 

[Strawberry]

Reccomend tank turnover is flow from powerheads and your return combined. Sump turnover is how often your system volume is run through your sump. Typically the reccomended sump turn over is 3-5 times your system volume unless you plan on running a specific filtration setup like the Triton method which calls for 10 times turnover.

Why does the triton method require higher turn over? I appreciate you taking the time to explain the difference between tank turnover and sump turnover. That makes a lot more sense.

 

[Silent]

I did not do this math but this might give you an idea of volume and pipe sizes.

 

[JoshH]

I’m trying to go with the smallest size possible, maybe just over thinking it a little. Because I have plenty of time to design it, I just want to make sure it’s correct. I guess that I could use schedule 40, but I thought it was only rated for drain pressure? I’m still learning a lot of these things, so please be patient with me lol

Schedule 40 is rated for I believe 120 PSI which is WAAAAYYYYYYYY beyond anything you'd see in this hobby as we don't want to create pressure, we want flow. And don't you worry about asking questions or needing clarification on things, that's why your here and why we're here, to get you going on the right path.

 

[Miller535]

Why does the triton method require higher turn over? I appreciate you taking the time to explain the difference between tank turnover and sump turnover. That makes a lot more sense.

The triton method requires a refugium section that I believe is 25% of tank volume, as this is their main method of filtration. 10% is what they came up with contact time for the water and the macro in the refugium. I personally have always shot to run 10%.

 

[Strawberry]

I did not do this math but this might give you an idea of volume and pipe sizes.

Thanks for the chart. I did do my calculations using schedule 80 which could be partly responsible for some of the flow rates being off. I was trying to apply the principle of overall water pressure from the system (using gravity, SG of water, and vertical dimension from water level). To see how that would affect it. For example, a 5 gallon water jug fills a cup faster when it is full than it does when it is nearly empty. The holes in this design being on the bottom should be more efficient than your typical tank drilled on the side. Not sure where I went wrong here lol

 

[Strawberry]

Schedule 40 is rated for I believe 120 PSI which is WAAAAYYYYYYYY beyond anything you'd see in this hobby as we don't want to create pressure, we want flow. And don't you worry about asking questions or needing clarification on things, that's why your here and why we're here, to get you going on the right path.

I appreciate your help! I should have looked at the PVC requirements more. What about a submersible return pump, rated for 1200 gph? I know you have to account for head loss and pressure loss through fittings, and then calculate psi. Even if it was plumbed in with schedule 40 it wouldn’t exceed that limit?

 

[Strawberry]

The triton method requires a refugium section that I believe is 25% of tank volume, as this is their main method of filtration. 10% is what they came up with contact time for the water and the macro in the refugium. I personally have always shot to run 10%.

Seems like it could get kind of tricky when you’re trying to calculate contact time. I know some of my stuff is way off but I have good intentions and I’m on the right path lol there’s no way I’d pay that kind of cash for something I could build or have fabricated locally for way less.

 

[Silent]

I appreciate your help! I should have looked at the PVC requirements more. What about a submersible return pump, rated for 1200 gph? I know you have to account for head loss and pressure loss through fittings, and then calculate psi. Even if it was plumbed in with schedule 40 it wouldn’t exceed that limit?

Not a chance