How to calculate overflow rate.

Joe Batt · May 21, 2018

I am planning a new aquarium for a few months time. I was thinking of the RedSea 650 Peninsula and converting the sump to Triton.

I am just a little concerned as to the overflow rate that is available back into the sump from the tank. Is there a calculation I can run to check the maximum overflow I would get?

Dr. Reef · May 21, 2018

It all depends what pump are you using and how much water it's going to push because pump and overflow basically go hand-in-hand.
HOB overflows are rated by manufacturers according to their shape size and ability to drain water. But if you are going to have a drilled tank with bulkhead then the following applies.

1/2" drains 420gph
3/4" 660 gph
1" 960 gph
1.25" 1500gph
1.5" 2100gph

Match that to your return pumps capacity after headloss to figure what size works best.

For example a regular reef dart can push 3600 gph at 0 feet and after 4 ft 3035gph.
So if you had a dart as return you would need 2x drains of either 1.25" or 1.5". In that example I would personallygo with a bit bigger than my pumps capacity so I'll choose 1.5".

Joe Batt · May 21, 2018

I am wanting to use the Triton method which requires around 10x +/- display volume. I am looking at the RedSea peninsula 650 and wanting to work out what the maximum return to the sump would be. The return pump itself isn't a problem however if I cant get near to the 10x back down the drain to the sump then there is no point in the RS 650

Dr. Reef · May 21, 2018

I understand but the flow that is coming down is totally dependent on what the pump is pushing up
For example if you have a 3000 gallon pump 3000 will come down if you have a 500 gallon per hour pump only 500 will come down so what is the total volume of the tank let's try to figure that out from there

Joe Batt · May 21, 2018

I disagree. The downflow to the sump will have to depend on the size of the pipe returning to the sump plus the pressure / height of the water. So long as the return pump is less than the maximum downflow and I can tune the downflow down to match the return pump I am sorted.

If I have a 3000 gph pump and a downflow that can only cope with 2000 gph then I have to reduce the pump to meet the downflow maximum or I will flood the house. If I have a 500 gph pump and a downflow that can cope with 2000gph I will have no problem.

With the 650 the display size is 140g so I need a downflow that can at least cope with 10x 140gph... ie 1400gph +/- . The downflow has a fixed maximum on the Red Sea 650 Peninsula because its an off the shelf tank. The downflow can be tuned downwards, so as long as its rated at a maximum of 1400gph (ish +/-) or more, I can work with it by sizing my return pump. If its maximum is 500gph, for example, then I cant.

This is why I am trying to find the maximum that the RS 650 Peninsula downflow can handle.

Dr. Reef · May 21, 2018

you have it totally opposite. you start with pump and then see what gph is being delivered after head loss. then you make sure the drain is a size up than what pump can push. water drain with gravity not with pressure.
down will always be dependent on the pump pushing up given all pipe sizes are according.
i already mentioned the sizes of pvs with their natural flow under gravity. you can go from there.
what size bulkhead is on the down/drain of the tank?

Dawsokj1988 · May 21, 2018

Joe Batt said:
I disagree. The downflow to the sump will have to depend on the size of the pipe returning to the sump plus the pressure / height of the water. So long as the return pump is less than the maximum downflow and I can tune the downflow down to match the return pump I am sorted.

If I have a 3000 gph pump and a downflow that can only cope with 2000 gph then I have to reduce the pump to meet the downflow maximum or I will flood the house. If I have a 500 gph pump and a downflow that can cope with 2000gph I will have no problem.

With the 650 the display size is 140g so I need a downflow that can at least cope with 10x 140gph... ie 1400gph +/- . The downflow has a fixed maximum on the Red Sea 650 Peninsula because its an off the shelf tank. The downflow can be tuned downwards, so as long as its rated at a maximum of 1400gph (ish +/-) or more, I can work with it by sizing my return pump. If its maximum is 500gph, for example, then I cant.

This is why I am trying to find the maximum that the RS 650 Peninsula downflow can handle.

I don't have the exact flow numbers but I'm running a varios 8 pump on my reefer 750. I notice an increase in flow into my sump when I switch between 1-5 settings (meaning it's not capping at some point due to overflow restrictions). I modified my sump as well by removing the filter sock baffling (and installing a clarisea sk-5000).

Dawsokj1988 · May 21, 2018

Dr. Reef said:
you have it totally opposite and wrong. you start with pump and then see what gph is being delivered after head loss. then you make sure the drain is a size up than what pump can push. water drain with gravity not with pressure.
down will always be dependent on the pump pushing up given all pie sizes are according.
i already mentioned the sizes of pvs with their natural flow under gravity. you can go from there.
what size bulkhead is on the down/drain of the tank?

His concern is how the reefer series are built. They come pre-drilled and pre-plumbed. It's a single overflow box, not dual overflows. The concern on the larger tanks (650, 750) is the overflow restrictions due to the design. I'm guessing he's wanting to make sure the flow doesn't cap out at some point (meaning he'd get the same flow from a 1000 gph pump as he would from a 2000 gph pump).

Mr. Bill · May 21, 2018

FWIW, Red Sea recommends a 7000lph pump which is greater than 10x for the 650, so the included drain would be able to handle at least that, but probably more. The overflow skims from the surface and maintains the water level in the DT, so your drain cannot outpace the return.

Dr. Reef · May 21, 2018

Mr. Bill said:
FWIW, Red Sea recommends a 7000lph pump which is greater than 10x for the 650, so the included drain would be able to handle at least that, but probably more.

i saw on their website that they recommend 1850 gph pump i am assuming they probably have a single 1.5" drain which is capable of handling 2100 gph drain at natural gravity.
can someone verify how many drains it has and what size pvc.

Dr. Reef · May 21, 2018

Dawsokj1988 said:
His concern is how the reefer series are built. They come pre-drilled and pre-plumbed. It's a single overflow box, not dual overflows. The concern on the larger tanks (650, 750) is the overflow restrictions due to the design. I'm guessing he's wanting to make sure the flow doesn't cap out at some point (meaning he'd get the same flow from a 1000 gph pump as he would from a 2000 gph pump).

got it, the only way to find out the true drain capacity is to find out how many drains there are on the back of the tank and what pvc size. if someone can provide the info we can calculate the pump size.

Dr. Reef · May 21, 2018

ok a little digging online shows it has a main drain of 32mm (1.25") and an emergency drain of 25mm(1")
so the max you can drain out of the main drain is 1500gph and from emergency drain another 960gph

Mr. Bill · May 21, 2018

Dr. Reef said:
got it, the only way to find out the true drain capacity is to find out how many drains there are on the back of the tank and what pvc size. if someone can provide the info we can calculate the pump size.

Main drain is 32mm, emergency drain is 25mm; return plumbing is 25mm.

https://www.bulkreefsupply.com/reef...2wslHtnO40hGinbSgNHevddXBqJ_6MCcaAsq0EALw_wcB

Dr. Reef · May 21, 2018

Mr. Bill said:
Main drain is 32mm, emergency drain is 25mm; return plumbing is 25mm.

https://www.bulkreefsupply.com/reef...2wslHtnO40hGinbSgNHevddXBqJ_6MCcaAsq0EALw_wcB

Dr. Reef said:
ok a little digging online shows it has a main drain of 32mm (1.25") and an emergency drain of 25mm(1")
so the max you can drain out of the main drain is 1500gph and from emergency drain another 960gph

Mr. Bill · May 21, 2018

Great minds think alike. :D

Dr. Reef · May 21, 2018

Mr. Bill said:
Great minds think alike. :D

yes they do lol
thank you...
red sea recommends 1850gph pump max so after head loss they figure a 1500 gph drain should be able to handle it and worse case there is additional 960gph emergency drain.

Joe Batt · May 21, 2018

Dawsokj1988 said:
His concern is how the reefer series are built. They come pre-drilled and pre-plumbed. It's a single overflow box, not dual overflows. The concern on the larger tanks (650, 750) is the overflow restrictions due to the design. I'm guessing he's wanting to make sure the flow doesn't cap out at some point (meaning he'd get the same flow from a 1000 gph pump as he would from a 2000 gph pump).

Exactly :) I'm glad you understand what I mean. I need the drain to be able to handle at least 1400gph for it to meet the Triton requirements (a little less is OK) If It for example is capable of handling 3000gph, great then so long as the return pump when head pressure has been taken into account can deliver 1400gph I am fine. As you say they recommend 1850 gph so that will fit in nicely at more than 10x display size, and if they recommend it, then drain must be able to cope with it or it would flood.

Dr. Reef · May 21, 2018

Joe Batt said:
Exactly :) I'm glad you understand what I mean. I need the drain to be able to handle at least 1400gph for it to meet the Triton requirements (a little less is OK) If It for example is capable of handling 3000gph, great then so long as the return pump when head pressure has been taken into account can deliver 1400gph I am fine.

sorry i wasnt understanding at first. the tank comes with a drain size of 32mm which can drain 1500gph

Joe Batt · May 21, 2018

Found this too, which helps also as it has a calculator on it

http://www.beananimal.com/articles/hydraulics-for-the-aquarist.aspx

Joe Batt · May 21, 2018

I have the 350 and the head height is around 41 inches, so since the 650 is larger the head height should be at least that. That gives me approximately 3400 gph :) More than enough :)