Figuring Overflow Gph Capacity

[JustAHobbiest]

I have a beautiful Oceanic 180g Bowfront. Plan on starting a build thread here in the future. It has been in my basement for about a 18 months. As everyone starts out, I'm kinda new to saltwater and currently in cram mode as far as info. Iv been researching everything Reef related. I can't find anywhere a formula to calculate Gph for overflows I have two overflows in either end of tank. Thanks in advance.

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[Vinny Kreyling]

No calculator, too many variables. Sumps should be as big a possible for extra water volume because most run "around" 1/2 full. Overflow can be controlled in a few ways, keep the returns high in the water column & or drill a siphon break in the return line "just" under the water level facing downward.
Drain down is something to be worked out when you 1st start the system.
Fill the tank to the overflow teeth but not draining, the sump should be close to full.
Start the pump & see where the water level drops to in the sump, this is your MAX water level. Slowly remove water from the system until just before the pump starts to suck air. This is your MIN water level. You should run normally in the middle, or slightly above of those 2 marks and you will not overflow the system.

 

[JustAHobbiest]

Thanks for the advice was just trying to get ball park idea in what side pump I needed plan on a 40B for sump that big enough?

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[Vinny Kreyling]

I would say marginal, especially if you plan on a tank upstairs with the sump in the basement. I have an 80 gallon sump on a 250 & it runs around the 35 gallon mark.
No basement so it's under the tank.

 

[BlackTip]

I have a beautiful Oceanic 180g Bowfront. Plan on starting a build thread here in the future. It has been in my basement for about a 18 months. As everyone starts out, I'm kinda new to saltwater and currently in cram mode as far as info. Iv been researching everything Reef related. I can't find anywhere a formula to calculate Gph for overflows I have two overflows in either end of tank. Thanks in advance.

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Very good question and extremely important. The capacity of the overflow is determined by the weir length and the distance from the overflow box top to the top of the tank. When water fall into the overflow box, the water rise and create a wall before it drops to the overflow. The maximum capacity is when this wall rise just before it overflow from the tank to the floor. Obviously, you don't want to operate at maximum capacity, but far below it.

Her is a good calculator to start:
http://irrigation.wsu.edu/Content/Calculators/Water-Measurements/Rectangular-Contracted-Weir.php

 

[mcgyvr]

In general you shoot for a flow rate through the sump at 5-10X display tank volume..
And total flow in a tank (return + powerheads) at 30-100X.. With the higher being for high flow SPS corals,etc...

For 180G I'd just get a pump capable of 1800GPH.. You can always put a T on the output to dump some right back into the sump to adjust flow through the display or just get a DC pump thats adjustable. (<-- best option)..
Ecotech has some neat (lowish cost) Vectra series pumps that look pretty nice and quite a few seem to be going with.. Jebao has some too DC/DCT series that are "lower quality/price" but still decent pumps that are adjustable

 

[pisanoal]

Very good question and extremely important. The capacity of the overflow is determined by the weir length and the distance from the overflow box top to the top of the tank. When water fall into the overflow box, the water rise and create a wall before it drops to the overflow. The maximum capacity is when this wall rise just before it overflow from the tank to the floor. Obviously, you don't want to operate at maximum capacity, but far below it.

Her is a good calculator to start:
http://irrigation.wsu.edu/Content/Calculators/Water-Measurements/Rectangular-Contracted-Weir.php

^^This

Not meaning to offend anyone, I think the other posters missed the intent of the question. They gave good advice, just not what I understand from the OPs post. There actually are formulas to calculate how much flow your overflows can handle. The link posted here will tell you how much flow your weir can handle. Then you would also need to know what diameter bulkheads you have to find out how much water they can pass. For the above calculator, you will need to know how many teeth you have in both weirs, and how wide each tooth opening is. Width times the number of teeth will give you your length for the posted calculator. For height, I would measure the height of the teeth and use that. Anything over will be added capacity in case of pluggage. You want some safety built in. For the standpipe capacity https://flexpvc.com/Reference/WaterFlowBasedOnPipeSize.shtml (use the green column). Pipe diameter is your bulkhead diameter, or where ever your smallest piece of pvc pipe is. (Doesn't matter if you run 4" pvc if your bulkhead is only 1/2", that is where your max flow is limited as it is directly related to cross sectional area).

Keep in mind, you will want the system running some where around <50% for emergency purposes. Each standpipe should be able to handle your total return flow by itself if only using 2, just in case one should become completely plugged.

 

[Flaring Afro]

^^This

Not meaning to offend anyone, I think the other posters missed the intent of the question. They gave good advice, just not what I understand from the OPs post. There actually are formulas to calculate how much flow your overflows can handle. The link posted here will tell you how much flow your weir can handle. Then you would also need to know what diameter bulkheads you have to find out how much water they can pass. For the above calculator, you will need to know how many teeth you have in both weirs, and how wide each tooth opening is. Width times the number of teeth will give you your length for the posted calculator. For height, I would measure the height of the teeth and use that. Anything over will be added capacity in case of pluggage. You want some safety built in. For the standpipe capacity https://flexpvc.com/Reference/WaterFlowBasedOnPipeSize.shtml (use the green column). Pipe diameter is your bulkhead diameter, or where ever your smallest piece of pvc pipe is. (Doesn't matter if you run 4" pvc if your bulkhead is only 1/2", that is where your max flow is limited as it is directly related to cross sectional area).

Keep in mind, you will want the system running some where around <50% for emergency purposes. Each standpipe should be able to handle your total return flow by itself if only using 2, just in case one should become completely plugged.

You also can use this for the beananimal setup.
http://www.beananimal.com/articles/hydraulics-for-the-aquarist.aspx

 

[pisanoal]

That's for any setup. That's must a general fluid mechanics equation for water falling from a a tank through a pipe. I would just use the guidelines for pvc diameters. They will be close enough.

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[Sk8r]

I'm using a 30 gal sump nicely on my 100 gal with a 2350 gph pump in the basement, which is about 15 feet of head. Roughly. If I had a 3000 gph pump, I'd put a gate valve in the return line, which lets you dial down the flow to something comfortable for the critters as well as for the capacity of the downflow line.

 

[BlackTip]

The OP is asking about how much water the OVERFLOW BOX can handle. He is not asking about the proper flow rate nor pipe capacity. Each overflow box can handle so much water, before the water overflow the tank itself. See my post above.

 

[Flaring Afro]

That's for any setup. That's must a general fluid mechanics equation for water falling from a a tank through a pipe. I would just use the guidelines for pvc diameters. They will be close enough.

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No, it's only for a siphon drain that isn't sucking in any air at all.

 

[pisanoal]

Any standpipe will go full siphon if the water level gets high enough. Unless it's modified to specifically not. If he plans on running a bean animal set up or similar then he needs that calc. If he is not, then that calc does him no good as he does not want his standpipe to go full siphon.

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[JustAHobbiest]

I will have to do some good digging and reading on all the links posted thanks in advance. If it does help, each overflow has two 1.5" holes at the bottom and I plan on running some form of herbie. It's my understanding that the bean animal only works optimally with a C2C box. Any input on my overflow method would be greatly appreciated. I do have 3 bulkheads in the back of tank between the overflow boxes I plan on using for returns. Also someone correct me if I'm wrong but the return pump in your sump controls the gph through the sump not just the gph in the DT. I dont want an abundance of flow through the sump probably 1000 gph on the high end. Thanks again for the quick replies I hope some of you stick with me as I gather more info I know I will have a couple more problems turn up.

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[Vinny Kreyling]

If you only plan on 1000 GPH 1.5" drains are too large & the boxes will drain down giving you a surge & loud overflows. For a Herbie drain I would make them no larger than 1" with a Gate Valve on each. The emergency drain can be 1.5", you want to hear that one.
Use power heads for extra flow in the tank.

 

[mcgyvr]

The OP is asking about how much water the OVERFLOW BOX can handle. He is not asking about the proper flow rate nor pipe capacity. Each overflow box can handle so much water, before the water overflow the tank itself. See my post above.

See post #3...
Sounds like he is asking for a recommendation on pump size for his tank/40G sump and not theoretical limits on how much the box can handle... See my post above

was just trying to get ball park idea in what size pump I needed

 

[pisanoal]

The OP is asking about how much water the OVERFLOW BOX can handle. He is not asking about the proper flow rate nor pipe capacity. Each overflow box can handle so much water, before the water overflow the tank itself. See my post above.

I'm not sure why you are offended, I was agreeing with your post and explaining how to use your link to calculate the flow over the weirs... And if you read his post, he wants to know how much his overflow will handle, not just overflow box. Doesn't matter how much the box will handle if the pipes don't handle enough, and the same is true the other way around. Overflow=weir + standpipes. The link you posted is good information for weir flow calculation.

 

[pisanoal]

I will have to do some good digging and reading on all the links posted thanks in advance. If it does help, each overflow has two 1.5" holes at the bottom and I plan on running some form of herbie. It's my understanding that the bean animal only works optimally with a C2C box. Any input on my overflow method would be greatly appreciated. I do have 3 bulkheads in the back of tank between the overflow boxes I plan on using for returns. Also someone correct me if I'm wrong but the return pump in your sump controls the gph through the sump not just the gph in the DT. I dont want an abundance of flow through the sump probably 1000 gph on the high end. Thanks again for the quick replies I hope some of you stick with me as I gather more info I know I will have a couple more problems turn up.

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Yes, your return pump controls the flow through your sump as well. What ever you pump from your sump to your display has to go down the overflows back through the sump. Closed system, so return pump flow=sump flow unless you do as another poster recommended and T off the return with some of the flow going back to the sump. Whether or not that's a good idea depends on your sump setup. Works well if you want to run media reactors without an extra pump. mcgyvr also posted about total DT flow which would be your return flow + powerheads in the tank.

One thing to note, if you look to buy a 1000gph pump, make sure you account for head loss. For example, if your pump is in the basement, you will have 10-15feet of head pressure to overcome which will significantly effect the pumps flow rate, while if its just below the tank, it will likely be around 3-4 feet. Most pumps have a chart that will show you approx. flow for different head losses. Most of the time, head loss = the vertical height your pump has to overcome, unless you have a lot of 90's in your plumbing or its a remote sump in a garage or something.

 

[JustAHobbiest]

Just to play Devils advocate here. What are the pros and cons to higher flow in the sump. Will have a fuge with 3in sand bed and algae no live rock. Higher flow being upwards of say 1500-2500 low flow being 500-1000

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[pisanoal]

Some say you want a low flow through the refugium to allow some retention time. Depending on how you construct your fuge (ie sand/mud or just LR rubble, and a screen to keep your macro in place), it might disturb your substrate if flow is too high. FYI I recommend the latter, no reason in my opinion to use 3" of sand unless you are going bare bottom and want some sand critters in the system. Retention time for me is a non-issue. If you have a high flow, your macro is getting the full concentration of nutrients in your tank all the time and able to absorb it at the most efficient rate. Also will help keep detritus from settling there and making it a cesspool. On the other hand, some say you want detritus to settle somewhere in your sump if you aren't using a filter sock so it can be siphoned out easily on water changes, so that would be a pro for lower flow (I'm in this camp as long as it settles in an easy to clean area). There are others Im leaving out, im sure someone will be happy to point out for me.