Connect Two Tanks

[unchaotic]

First off, I'm still in the planning stage so there's no livestock or water to worry about yet.

I've got two tanks that will be side by side and are currently not drilled; a 7 foot 200 gallon and a 4 foot 95 gallon wave. The 200g will be a mixed reef and the 95g will be a display refugium. I want the dirty water from the 200 to go through the 95 before any other filtration.

The tanks are both 24" tall and I was wondering if they could simply be drilled at the same height on adjoining ends and then connected with bulkheads and some flexible hose (to allow some give)? I was thinking of putting a weir in the 200g and probably doing two holes for redundancy similar to an external overflow box. Then the 95g would have a weir and overflow box with a bean animal setup to go to the sump.

I've tried finding info on such a thing and just keep finding references to water bridges. Am I way out of left field here or should this be possible?

 

[EeyoreIsMySpiritAnimal]

I don’t think this would be too difficult - people add refugiums to sumps in this manner all the time.

 

[unchaotic]

I don’t think this would be too difficult - people add refugiums to sumps in this manner all the time.

So I'm just a freak for wanting to do it with display tanks?

 

[Soren]

That plan should work well, and a weir like a typical overflow would be a good idea.

The plan for my setup is different but has some similarities. My plan is a 90-gallon display (90DT) with a 75-gallon mangrove lagoon (75ML) along the same wall end-to-end to the 90, and a 75-gallon macroalgae-refugium sump (75MR). Since there is a height difference, I have typical overflows in between the 90DT and 75ML and the 75ML and 75MR. The top of the 90DT is highest with a step down to the 75ML and another step down to the 75MR directly under the 90DT. Return is from 75ML up to 90DT.

...so you are not a freak for this consideration in my opinion!

 

[CMMorgan]

I think you are just googling the wrong thing. @Erin1971Texas is right. You really just need an overflow from the 200 to feed into the 90 and then the return from the sump to go back to the 200. Just make sure you have an emergency overflow built in. If that 200 overfills that 90... you are going to have a mess on your hands.

 

[pledosophy]

IME/IMO It will be much easier and better long term if you just plumb them both to a common sump.

Split your return into two, and plumb a line to each. You can put a gate valve on the plumbing to adjust the flow to each.

If you are interested in maximizing your pods I would have your display refugium dump into the sump after your filters, not before.

I have done this on seperate sides of the wall how I described above and was very happy with it. Also makes it easy to disconnect the tanks if you ever need to for any reason by just closing the valve to one of the tanks. Less failure points.

 

[Rjramos]

Gravity works great vertically but horizontally, there has to be a difference. The less that difference is,the less the water will move across. Also, the sump has to be able to hold the overflow capacity of both tanks. I work with dual sumps in the cabinet and have such bulkhead to bulkhead connections from one sump to another. There has got to be a significant difference in height or it just won’t flow as needed.
These 2 60 gal. Share a common refugium and sump below. Water from both to the refugium which is elevated and feeds into a lower sump where the pump draws and feeds both tanks.

 

[CMMorgan]

@pledosophy

 

[unchaotic]

I think you are just googling the wrong thing. @Erin1971Texas is right. You really just need an overflow from the 200 to feed into the 90 and then the return from the sump to go back to the 200. Just make sure you have an emergency overflow built in. If that 200 overfills that 90... you are going to have a mess on your hands.

I was thinking the overflow on the 95 would need to be big enough to handle a 200g at minimum. Then the bean animal approach sounds like the safest option to prevent overflows.

 

[CMMorgan]

I was thinking the overflow on the 95 would need to be big enough to handle a 200g at minimum. Then the bean animal approach sounds like the safest option to prevent overflows.

Yes - go bean... but I really really like @pledosophy's idea. It makes the most sense.

 

[mdb_talon]

I like your original idea. One tank will drain to the other with no issues in my experience assuming a properly sized bulkhead between the two. I have a tank setup this way myself with just a bulkhead in the side of one tank and it flows into my frag tank....which then flows to my sump.

 

[Pistondog]

I have a 75g dt + 20g dt both plumbed to 30g sump.separate return pumps.
Works great.

 

[mdb_talon]

Gravity works great vertically but horizontally, there has to be a difference. The less that difference is,the less the water will move across. Also, the sump has to be able to hold the overflow capacity of both tanks. I work with dual sumps in the cabinet and have such bulkhead to bulkhead connections from one sump to another. There has got to be a significant difference in height or it just won’t flow as needed.

If this were the case everyone would have issues with their overflow. Remember it has to flow horizontally through the teeth on a standard overflow before it gets to the vertical drain.

 

[Montiman]

The only problem I foresee is that in order to get surface skimming in the first tank you need to have the water level inside the overflow box be lower than the display level. However if the overflow is connected to the 2nd tank then these water levels will naturally equalize. Since both tanks are the same height this presents a problem because the water level in the weir box will naturally shift to the display height in the second tank, which will be the same as the display height in the 1st tank meaning no surface skimming.

You would need the 1st tank to be slightly higher in order to get surface skimming in the first tank.

I would rather just plumb both tanks to the same sump. This is the most proven way to plumb 2 tanks together.

 

[Soren]

If this were the case everyone would have issues with their overflow. Remember it has to flow horizontally through the teeth on a standard overflow before it gets to the vertical drain.

It's not so much a question of the direction of water movement as a difference in water surface height between the connected tanks. If there is a height difference, water pressure should allow for flow. If they are at the same height, there will not be any noticeable flow between tanks, as @Rjramos mentioned.

 

[codee]

I’m planning something similar, but the display ‘fuge is mid height, vertically, between DT and sump. I’m also going to add some T’s and ball valves so I can adjust the plumbing later without too much hassle.

For two tanks at the same height, seems best to plumb both into sump.

 

[unchaotic]

So what I'm getting from this discussion is that I should drop the 95g down about a foot, and leave the space above it largely open for mangroves.

 

[mdb_talon]

It's not so much a question of the direction of water movement as a difference in water surface height between the connected tanks. If there is a height difference, water pressure should allow for flow. If they are at the same height, there will not be any noticeable flow between tanks, as @Rjramos mentioned.

The drain is in the second tank....water always find equilibrium so yes they will remain roughly the same height....it does this because water flows between tanks . If the theory is it wont flow between tanks because the height is the same then there is a logic problem. They only stay the same height because water flows between them.

 

[DCR]

There will be a difference in the water level between the two tanks. How much will depend on the flow rate, the size of the bulkheads, and the arrangement of any weirs. Not sure what size bulkheads you were thinking but they need to be large - like three 2" or so. If you install weirs, the crest over each weir needs to be considered. The difference in water level can easily be an inch or more. I agree with a previous poster that it is better to just drain to a common sump and pump back from the sump to both tanks.

 

[Chrysemys]

If you bulkhead two tanks together the hydraulics works as if it was one tank. Put the overflow in the 95. The height of this will set the water level in both tanks. Ensure the bulkhead between the two will handle all the flow coming into the 200. It is really pretty simple.
The height of the bulkhead in irrelevant as long as it is completely submerged. Screen if you are concerned about livestock migrating between the 2. Keep in mind screening will reduce possible flow.