Need help with Sump and Overflow

[BitFix]

I plan on adding a sump to an freshwater tank that I already own so as to increase the water volume to eventually turn it into a reef tank. But since the tank is so small I didn't want to add a overflow tower, since it would take too much space and would rather adding an overflow box. Right now I need help trying to add a herbie style overflow to an acrylic overflow box. Also could someone explain me how to determine water flow to and back from the sump? I will add a return pump of about 400gph, but need help determining how much water drains to the overflow. How do I make sure neither the DT or the sump will overflow?

Here's a rough sketch I make on Paint (sorry for paint):

 

[Flippers4pups]

Bump

 

[Idoc]

To determine if there is enough space in the sump for a pump shutdown, all you have to do is calculate the amount of water that would drain back into the sump until the siphon is broken. On my return line, i drilled a hole in the line 1" under the water line. So, i have 48"x18"x1" of tank water that will go back into the sump... along with a couple gallons in the overflow box and pipes. Then calculate the space/area in the sump that is above your current sump water lines to determine how much extra water your sump can hold before it overflows. If you're sump space is greater than the amount that will flow back into the sump, then all is well and you will never have a flood!

 

[BitFix]

To determine if there is enough space in the sump for a pump shutdown, all you have to do is calculate the amount of water that would drain back into the sump until the siphon is broken. On my return line, i drilled a hole in the line 1" under the water line. So, i have 48"x18"x1" of tank water that will go back into the sump... along with a couple gallons in the overflow box and pipes. Then calculate the space/area in the sump that is above your current sump water lines to determine how much extra water your sump can hold before it overflows. If you're sump space is greater than the amount that will flow back into the sump, then all is well and you will never have a flood!

Although that will be very helpful, that isn't my main issue, my problem is that I don't know if my oveflow will end up draining not enough or too much water and my pump will overflow the display tank or the sump itself.

 

[DLHDesign]

You will want a gate valve (not a ball valve, if possible - gate valves are easier to tune) on the main return line. That will allow you to control the flow back to your sump - which is really only important to reduce the noise produced.
That should be all you really need. With a 400gph return pump, you shouldn't need to reduce the return flow to fit the drain lines - 1" schedule 40 PVC being gravity fed can handle around 960gph. But if you would like to be able to control the return flow, you can add another gate valve to the return line. That; or use a DC pump which allows the flow rate to be configured based on the power provided.

 

[laverda]

There are flow calculators on RC and elsewhere that estimate flow over an over flow and through different drain pipe sizes. For your pump you need to look at a flow chart for it to see what expected flow will be at your tanks height. In addition you can use an adjustable DC pump or put a ball or gate valve on the return pump. The water level in your tank will primarily be controlled by your overflow. Your drain Lin’s should be sized to handle as much flow as your overflow can handle.

 

[BitFix]

You will want a gate valve (not a ball valve, if possible - gate valves are easier to tune) on the main return line. That will allow you to control the flow back to your sump - which is really only important to reduce the noise produced.
That should be all you really need. With a 400gph return pump, you shouldn't need to reduce the return flow to fit the drain lines - 1" schedule 40 PVC being gravity fed can handle around 960gph. But if you would like to be able to control the return flow, you can add another gate valve to the return line. That; or use a DC pump which allows the flow rate to be configured based on the power provided.

So if I add a gate valve in the drain line from the DT to the sump I'll be able to balance the water level in both?

 

[theMeat]

Me thinks you’re not understanding that the size/gph of return pump determines how much water overflows back to sump

 

[BitFix]

Me thinks you’re not understanding that the size/gph of return pump determines how much water overflows back to sump

I'm definitely not

 

[Idoc]

Although that will be very helpful, that isn't my main issue, my problem is that I don't know if my oveflow will end up draining not enough or too much water and my pump will overflow the display tank or the sump itself.

Gotcha ya! I mis-understood your question, lol. Your overflow should have 2 drain lines, correct? One for full siphon and one for an emergency drain?

Just to give you some perspective when i tested my system... i have a Varios6 DC return pump that can push around 1050gph-1200gph max with a head pressure height of 4 to 5 feet. I turned my pump on 100% and my full siphon drain line in the overflow handled it all with a 1" pvc return line. The emergency 1" drain line didn't even need to be used. So, if you are using a 1" drain line, you should be fine easily without problems. Hopefully that answers the question, lol.

Also... use a gate valve on the drain line, not a ball valve!

 

[Mikeneedsahobby]

I'm definitely not

So if I add a gate valve in the drain line from the DT to the sump I'll be able to balance the water level in both?

Let’s step back a bit. The overflow and drain line will only return water to the sump at the same rate as the pump pushes water into the tank for the sump. You do not balance them. The drain must be capable of more flow than the pump but it runs equal to the pump. You balance the drain so that it will be quiet.

Here is some foundation reading material.
http://www.reeftime.com/reef-articles/how-does-an-overflow-box-work/63.htm
https://www.bulkreefsupply.com/choosing-an-aquarium-overflow

 

[theMeat]

I'm definitely not

Ok. The valve makes it so that one drain line is full siphon , which = quiet.
You should watch a video on how to start/purge/plumb a “bean animal” or “herbie” overflow.

 

[BitFix]

Let’s step back a bit. The overflow and drain line will only return water to the sump at the same rate as the pump pushes water into the tank for the sump. You do not balance them. The drain must be capable of more flow than the pump but it runs equal to the pump. You balance the drain so that it will be quiet.

Here is some foundation reading material.
http://www.reeftime.com/reef-articles/how-does-an-overflow-box-work/63.htm
https://www.bulkreefsupply.com/choosing-an-aquarium-overflow

Ohhhh, now I get get it. Thank you so much, I didn't realize the pump makes the water level go up and the overflow drain. So I should place the overflow in the middle of where I want the water level to be, right?