Weir width and drain diameters ?

[Ridgeway Swiss]

OK I've plugged in the GPH into the calculator here on RC but want to make sure I understand the answers.

Based on 5000 gph it gives:

1) Linear overflow size at 76"
2) Drain pipe diameter at 2.92"

Surely a +6ft weir is way overkill ? Does anyone know the water bead thickness this is calculated on ? I plan a 52" overflow so assume that the water bead will just be higher, right ? or did I miss something in my simple assumption ? Also this doesn't of course factor in any weir comb reduction.

Also the drain pipe diameter suggests 2.92", I plan 3 x 2" drain pipes plus a safety 1.5", I guess I add this all up to make sure it's above the calculated value which in fact it's more than double.

Have I understood this correctly and what's the deal on the weir width ?

 

[thejuggernaut]

I bet the calculator is setup for a weir with teeth, a 5' long flat weir will flow ALLOT of water. Also the drains are open drains. If you make it a full siphon they will flow allot more water. It doesn't say how the numbers are calculated.

 

[uncleof6]

OK I've plugged in the GPH into the calculator here on RC but want to make sure I understand the answers.

Based on 5000 gph it gives:

1) Linear overflow size at 76"
2) Drain pipe diameter at 2.92"

Surely a +6ft weir is way overkill ? Does anyone know the water bead thickness this is calculated on ? I plan a 52" overflow so assume that the water bead will just be higher, right ? or did I miss something in my simple assumption ? Also this doesn't of course factor in any weir comb reduction.

Also the drain pipe diameter suggests 2.92", I plan 3 x 2" drain pipes plus a safety 1.5", I guess I add this all up to make sure it's above the calculated value which in fact it's more than double.

Have I understood this correctly and what's the deal on the weir width ?

Do not have any idea what data the calculator uses. Weir calcs are fairly straight forward however. It is not a bad estimate, as long as you realize that you need that length WITHOUT teeth. Teeth cut your functional length to 1/2 to 1/3.... so that is 6ft without teeth. And no that is not overkill, at all. It is called a Coast to Coast, and is the most efficient "weir" you can install in any given tank. (full width of the long side of the tank.) This is just one reason reef ready tanks are obsolete. Read the sidebar on Bean's website, for a little more detail as to why, and why tiny overflows are basically useless. The functional benefit of "teeth" or "combs" as some call the little devils, is nill. They are the result of a marketing hype "looks cool" thing, that folks have attached a great deal of significance to; they do more harm than good.

http://www.beananimal.com/projects/silent-and-fail-safe-aquarium-overflow-system.aspx

As far as pipe size goes, that calculator is way off. I don't know how it comes up with those figures, but they are mythical (if dealing with dursos) and far too low if dealing with siphons. A single 1.5" siphon will flow ~4600gph, (@36" drop) not accounting for some friction loss. A 3" pipe with the same drop flow ~18400gph, (not a typo—eighteen thousand,) not that you would want to do that. A 1.5" durso regardless of the drop, will flow ~350gph before it drives you out of your domicile due to noise issues, and instability. 3", don't know, but only enough to fill the pipe 1/4 full or less. For a 500 gallon tank, you would use a 2" siphon, with redundant backup =>

As long as you are on bean's site anyway, read the article to the left of the sidebar, to see how your planned drain system is... ...well off the hook.

 

[SGT_York]

using the francis formula

at 76" weir at 5,000 GPH your display tank will rise 1.4 inches. at 52" it will be 2.08 inches. Those numbers are higher than I expected, but quick check of my math seems to be right.

second the above. 1.5" siphon will be more than adequate.

 

[Gorgok]

using the francis formula

at 76" weir at 5,000 GPH your display tank will rise 1.4 inches. at 52" it will be 2.08 inches. Those numbers are higher than I expected, but quick check of my math seems to be right.

second the above. 1.5" siphon will be more than adequate.

I think you did something wrong there. A 1.4 inch rise on a 76" weir gets me to 22860 gph. A 1/2" rise gets me to 4980 gph.

Granted, i'm not doing the math myself, just using this: http://irrigation.wsu.edu/Content/Calculators/Water-Measurements/Rectangular-Contracted-Weir.php

 

[uncleof6]

using the francis formula

at 76" weir at 5,000 GPH your display tank will rise 1.4 inches. at 52" it will be 2.08 inches. Those numbers are higher than I expected, but quick check of my math seems to be right.

second the above. 1.5" siphon will be more than adequate.

1.5" for 5k gph? Including friction loss, unless the drop is longer than 3', it ain't gunna happen. It will flow < 4.6k which is the max theoretical according to Bernoulli, not accounting for friction losses.

 

[SGT_York]

Ah found it, typo in my conversion numbers! Just over a half of an inch at 76" and a bit shy of 3/4" for 52". (or 10.6/16" using the wsu link)


Uncle not quite sure, using a BA 1.5" at your 4.6K which only leaves 400 GPH to flow through the Open Channel??? I can't imagine a tank this size with less than a 3' drop.

 

[uncleof6]

Ah found it, typo in my conversion numbers! Just over a half of an inch at 76" and a bit shy of 3/4" for 52". (or 10.6/16" using the wsu link)


Uncle not quite sure, using a BA 1.5" at your 4.6K which only leaves 400 GPH to flow through the Open Channel??? I can't imagine a tank this size with less than a 3' drop.

First, you won't get 4.6K through a 1.5" bulkhead, @ a 36" drop, with 1.5" pipe. maybe around 4300gph...maybe less considering friction loss will be fairly high. But you are right, the drop will probably be longer than that. The last 300 I did, has ~56" of drop... However, what do you think the results of using 1.5" pipe for the flow you could get out of that? Max theoretical would be around 5.7k. Remember, these max theoretical values are for the bulkhead only, not with pipe attached.

Pump fed 1.5" starts to hammer itself apart at ~ 7500gph. One with casual exposure to all of this would tend to think wow, that should be more than enough. However, there is more to it than that, and the most that should be put through it (gravity driven; for minimal friction loss) is ~2100, but 3500gph is not too bad. Beyond that the friction loss starts getting out of hand, and you start getting some noise, with it increasing with the flow increase.

I told the OP 2", and even that is being generous for 5k. For least friction losses he should be using 2.5" (drains.) 2" on the return would probably be ok, depending on the pump outlet size; 2.5" would give a performance boost, within the capabilites of the pump.

Minimizing sizes with drains and even return lines is a bad idea. The concept is use large pipe. (Relatively speaking.) It does not change becasue this is the "fish hobby."

You want the flow through the open channel (with 1.5" pipe) to be kept below 350gph... unless your definition of silent is not really silent... 1.5" across the board, for 5k, is underkilled...

 

[SGT_York]

Yes upsizing is just about always a better method.

 

[Ridgeway Swiss]

Wow thanks guys, knowledgeable input like this is really appreciated.

To fill in some gaps:

Display is approx 700 gallons
Weir is planned at 52" long with weir comb, very wide cut but can remove if you convince me. It's an external weir box
Drains from this were planned as 3 x 2" plus 1 x 1.25", the main 3 x 2" will have ball valves and the 1.25" would be set higher and without valve as a back up
Intended flow from display is around 5000 gph
All pipes through the system will be 3 x 2" i.e. from 1st sump to second and then 3rd etc
Drop from bottom of weir box to 1st sump is small, it's around 12", this passes on to 2nd sump, about 2' drop and then to 3rd sump, around 1' drop.
The returns are 1.5" x 2, 1 for each pump.

I will put up a picture as it's easier to understand.

So it sounds like the drains are fine and that the water height would be around 3/4" if running without a comb, perhaps double with

 

[SGT_York]

The gaps do make some changes. As the dynamics of a siphon line the height of the water is from the top of the water to the top of the outlet. a 12" drop will slow down your siphon flow.

How wide are your teeth and how many do you intend on cutting, or provide spacing so it can be calculated. If you use 2/3" space open 1/3 hard teeth your weir drops from 52 to 34. Increasing the height in your display from less than 3/4 to over 7/8". That also means loss in surface skimming, but I'll won't anticipate how that will actually affect water quality. My biggest tank I've planned was a 300.

 

[Ridgeway Swiss]

Here's the layout:

[URL=http://s390.photobucket.com/user/Ridgeway_album/media/ScreenShot2014-12-11at210221.png.html][/URL]

 

[Ridgeway Swiss]

The planned weir comb is from Deltec. I can measure the one on my existing system as it's the same.

 

[uncleof6]

Wow thanks guys, knowledgeable input like this is really appreciated.

To fill in some gaps:

Display is approx 700 gallons

5k is pretty low for a system this size, you should be headed up to 7k. You can't get away with small hobby tank practices with the real tanks.

Weir is planned at 52" long with weir comb, very wide cut but can remove if you convince me. It's an external weir box

Easy: 52" "combed" weir = 26" effective length maximum. Most often it is going to be less. Physics is going to win, you need the full length of the back of the tank.

Drains from this were planned as 3 x 2" plus 1 x 1.25", the main 3 x 2" will have ball valves and the 1.25" would be set higher and without valve as a back up

What are you going to accomplish with three drains? Sounds like you are trying to install a broken BA system. Or some other machination that will not be safe. There is a right way to do this, and many many wrong ways...

Intended flow from display is around 5000 gph

Too low, see above.

All pipes through the system will be 3 x 2" i.e. from 1st sump to second and then 3rd etc

You need to rethink this. It is not going to work as you intend. Double gravity feeding anything is asking for a flood.

Drop from bottom of weir box to 1st sump is small, it's around 12", this passes on to 2nd sump, about 2' drop and then to 3rd sump, around 1' drop.

No. Although the drop (12") is long enough for ~15000 gph for 3 x 2" siphons, this is not going to be at all safe. And as I said before, there are limitations to what you should put through a pipe of any given size, which looks to be fine for 7000gph. However, with three 2" drains and a single 1.25" for back up is a flood begging to happen, as it will not handle the flow from a single occulded 2" pipe, let alone two. The statistical probability is irrelavent when discussing thousands of $ worth of damage.

The returns are 1.5" x 2, 1 for each pump.

First why two pumps? It is horribly inefficient, and will cost more to operate than running a single pump capable of delivering 7k at the given dynamic head height: ~ 72". You are wanting a hammerhead gold, but it won't do 7k, it will barely do 5300 at 6 feet, and won't get close with 1.5" pipe, (dynamic head, applied to the flow curve) estimating. To get to 7k you will need a Manta Ray, with 2" pipe on the outlet, 2.5" much better. It is a high head pressure pump, but the best you can do with reeflo... for 7k.

I will put up a picture as it's easier to understand.

Not really necessary. EDIT: But they do confirm what I have been saying. With an input voltage of 230(ABYZZ A200,) it makes sense you aren't in the USA . Pumps may be a bit harder to come by.

So it sounds like the drains are fine and that the water height would be around 3/4" if running without a comb, perhaps double with

Not really...

If there are errors in my calcs, I will take another look... I am getting old ya know...

 

[Ridgeway Swiss]

Thanks Uncle, appreciate your input.

I'll take each point as they are in the list:

5k is pretty low for a system this size, you should be headed up to 7k. You can't get away with small hobby tank practices with the real tanks.

7k is preferable I agree, this is around 10x t/o although I'm happy with between 7-10 x ratio.

Easy: 52" "combed" weir = 26" effective length maximum. Most often it is going to be less. Physics is going to win, you need the full length of the back of the tank.

The weir is the full length the back of the tank, well more or less. It's planned as 52" and the panel width there is 59" so it structurally can't be more, the other side is only a few inches longer.

What are you going to accomplish with three drains? Sounds like you are trying to install a broken BA system. Or some other machination that will not be safe. There is a right way to do this, and many many wrong ways...

The broken BA system, I don't understand what part of the 3 x 2" is broken, can you explain please.

Too low, see above.

You need to rethink this. It is not going to work as you intend. Double gravity feeding anything is asking for a flood.

Double gravity feeding ? do you refer to the fact that the water flows through a tiered system i.e. a stack ? how would this not work ?

No. Although the drop (12") is long enough for ~15000 gph for 3 x 2" siphons, this is not going to be at all safe. And as I said before, there are limitations to what you should put through a pipe of any given size, which looks to be fine for 7000gph. However, with three 2" drains and a single 1.25" for back up is a flood begging to happen, as it will not handle the flow from a single occulded 2" pipe, let alone two. The statistical probability is irrelavent when discussing thousands of $ worth of damage.

Can you explain why it will not be safe ?

First why two pumps? It is horribly inefficient, and will cost more to operate than running a single pump capable of delivering 7k at the given dynamic head height: ~ 72". You are wanting a hammerhead gold, but it won't do 7k, it will barely do 5300 at 6 feet, and won't get close with 1.5" pipe, (dynamic head, applied to the flow curve) estimating. To get to 7k you will need a Manta Ray, with 2" pipe on the outlet, 2.5" much better. It is a high head pressure pump, but the best you can do with reeflo... for 7k.

2 pumps as I want back up and it will also run other items via a manifold. A Hammerhead gold was a pump I used to run 15yrs ago since then I learnt about efficiency... This will be 2 x Abyzz A200's

Not really necessary. EDIT: But they do confirm what I have been saying. With an input voltage of 230(ABYZZ A200,) it makes sense you aren't in the USA . Pumps may be a bit harder to come by.

Not really...

If there are errors in my calcs, I will take another look... I am getting old ya know...

Overall I'm quite confused by this, so far it looked like a simple set up but it suggest here it's under sized and poorly thought through, I need to understand why.

Great input and this is the right time.

 

[SGT_York]

The horizontal runs you have will be siphon killers as well. Can you rethink the design and place the skimmer in a larger tank under the display and put the RO tank where the sump currently is. The refugium is easy enough to work with but the two horizontal runs will be flow killers. After seeing the drawing no way 1.5" pipe would work, and 2" will be a stretch depending on the angle and length of the horizontal runs (with two of them not a recommendable setup)

 

[uncleof6]

Thanks Uncle, appreciate your input.

I'll take each point as they are in the list:




Overall I'm quite confused by this, so far it looked like a simple set up but it suggest here it's under sized and poorly thought through, I need to understand why.

Great input and this is the right time.

Tomorrow will get back to this. Too involved right now.

 

[Ridgeway Swiss]

The horizontal runs you have will be siphon killers as well. Can you rethink the design and place the skimmer in a larger tank under the display and put the RO tank where the sump currently is. The refugium is easy enough to work with but the two horizontal runs will be flow killers. After seeing the drawing no way 1.5" pipe would work, and 2" will be a stretch depending on the angle and length of the horizontal runs (with two of them not a recommendable setup)

Actually the drawing isn't fully representative regarding the horizontals. These would be no more that 12" long and I could perhaps make the less if I position the weir bulkheads offset towards the sump stack, I see your point though.

Skimmers under tanks are something of the past TBH, I think it's fine for under cabinet stuff but I don't like things hidden away and at low levels etc. The pipe work is planned as 3 x 2" right the way through the system, I believe this is enough.

And yep having some angle on the horizontals makes sense, will incorporate that.

 

[Ridgeway Swiss]

Tomorrow will get back to this. Too involved right now.

Thanks, look forward to it.

 

[uncleof6]

Thanks Uncle, appreciate your input.

I'll take each point as they are in the list:

7k is preferable I agree, this is around 10x t/o although I'm happy with between 7-10 x ratio.

The more the better.

The weir is the full length the back of the tank, well more or less. It's planned as 52" and the panel width there is 59" so it structurally can't be more, the other side is only a few inches longer.

Well still get rid of the teeth. You won't have anything if they are left in the plan. Seriously, they started out as marketing hype, for aesthetics.

The broken BA system, I don't understand what part of the 3 x 2" is broken, can you explain please.

Well either that, or a broken herbie on steroids. BA system has three pipes. A siphon, an open channel, a dry emergency. (herbie has a siphon and dry emergency) The siphon takes most of the flow, the open channel a tiny portion of the total, the dry emergency sees no flow, except during startup and when the siphon is occluded. The dry emergency is the same size as the siphon, not smaller. Why? So the flow capacity is greater than the sum of the siphon and open channel flow rates.

You have three drains siphons? Or open channels (aka Dursos?) With dursos, your flow capacity is around 1200 gph, that ain't enough is it. With three siphons, see below. You have three drains, 1 dry emergency: broken.

Double gravity feeding ? do you refer to the fact that the water flows through a tiered system i.e. a stack ? how would this not work ?

Flow in equals flow out, sometimes the out is going to be over the sides of the container rather than down the drain. You cannot get a tiered gravity fed stack to flow equally in and out for each tank. You might get close, but one opps, or the "moon is closer today than yesterday" and you will have water all over the floor. Also the tanks in the lower stack need to use REAL drain systems not open pipes out the side. Intermediate tanks need to be pump fed and drain back to a common area, container, sump. If you can't pump feed them, get rid of them. Folks try to do this all the time. But these folks have trickles for flow, not 5k, but even at a trickle it is not working out the way they think it is.

Can you explain why it will not be safe ?

Can a 1.25" pipe handle the flow of a single 2" pipe? Can a 1.25" pipe handle the flow of two 2" pipes? Can a 1.25" pipe handle the flow of three 2" pipes? No! Unsafe. 1 siphon 1 dry emergency of equal or higher capacity. Basic siphon safety 101.

2 pumps as I want back up and it will also run other items via a manifold. A Hammerhead gold was a pump I used to run 15yrs ago since then I learnt about efficiency... This will be 2 x Abyzz A200's

A running pump is not a backup pump. A pump sitting on the shelf is a backup pump. What is the difference? If one running pump fails, it is more than likely the other pump that is running is close to failing as well. You end up with nothing running, and dead critters. A single larger pump with an identical pump held in reserve not running, is a backup system and more efficient. You still have more to learn about eficiency.:hammer:

Overall I'm quite confused by this, so far it looked like a simple set up but it suggest here it's under sized and poorly thought through, I need to understand why.

Great input and this is the right time.

It is all pretty straight forward, and a lot of it is common sense.

Really now... A single 2" bulkhead will flow ~9400gph with a 48" drop. Dialing back to 5000 gph, would put you in the mid sweet spot for 2" pipe flow wise, 7k at the upper end of the acceptable range... Three pipes: 2" siphon, 2" open channel, 2" dry emergency. Scratch the tier design concept, it won't work out well, increase the initial drop to at least 48", and have a system that works well! 2.5" pipe on 2" bulkheads would be better.

In the end you are way overcomplicating this, and nuclear powerplant systems are a real waste of time and money, and are no better than a simple straight forward tank/sump setup.

I don't know what your budget is, but using an average of $50 USD per gallon, a 700 gallon tank will cost you ~ $35,000 USD to set up right... Even a rock bottom of $35 USD per gallon, it is still 24.5k USD.