What is this? ...

[Saltyanimals]

I have a new tank. larger 72" tank with a center overflow. The top is what you expect with center overflows, but I noticed this bulkhead at the very bottom as you can see from the photo. What is it? It can't be a drain, since it would drain the entire tank down to about an inch above sand.. Can't be return because thats already comes out on top. Manufacture not responding so can't figure it out.

I'm hoping it's some kind of drain to help take in water towards the bottom of the tank so it doesn't only take from the surface level overflows. Any one have this on their tanks? Exist on both sides of the center overflow column.

 

[Idoc]

My overflow has a suction type inlet towers the bottom as well. It pulls in water/debri from the water column below the surface.

Mine actually pulls in the a small, thin compartment that then outputs somewhere higher on the inside of the overflow... I've never actually gone digging in there to find out where, though. But it had to do this otherwise the entire tank would drain into your sump when you turned off the return pump.

 

[cheelayqeelay]

Any plumbing to it on the inside of the overflow?

 

[Saltyanimals]

My overflow has a suction type inlet towers the bottom as well. It pulls in water/debri from the water column below the surface.

Mine actually pulls in the a small, thin compartment that then outputs somewhere higher on the inside of the overflow... I've never actually gone digging in there to find out where, though. But it had to do this otherwise the entire tank would drain into your sump when you turned off the return pump.

Bingo. That's my theory as well. It may be pulling in and sending it up higher inside the overflow component otherwise it would drain the entire tank. There is no actual plumbing in the center overflow except the 3 standards (drain, emergency and return).

if this was true, then these tanks are doing the bonus duty of pulling in water from the lower depths which is perfect for UV situations where parasites when free floating tend to stay lower in the tank. This is a real problem where folks have to plumb in an extra return to pull water from the bottom when sending to UV.

Problem is I'm not seeing a strong suction where I can visually see debris being drawn in. .. can you any on yours?

 

[Idoc]

Bingo. That's my theory as well. It may be pulling in and sending it up higher inside the overflow component otherwise it would drain the entire tank. There is no actual plumbing in the center overflow except the 3 standards (drain, emergency and return).

if this was true, then these tanks are doing the bonus duty of pulling in water from the lower depths which is perfect for UV situations where parasites when free floating tend to stay lower in the tank. This is a real problem where folks have to plumb in an extra return to pull water from the bottom when sending to UV.

Problem is I'm not seeing a strong suction where I can visually see debris being drawn in. .. can you any on yours?

Yes, I can see debri pulled into it on mine.

 

[Saltyanimals]

Yes, I can see debri pulled into it on mine.

I see some water movement, but wouldn't be any kind of forceful suction. Are you able to look inside (I think it's called a weir) and see what is at the other end of that bulkhead? What kind of tank do you have?

 

[Idoc]

I see some water movement, but wouldn't be any kind of forceful suction. Are you able to look inside (I think it's called a weir) and see what is at the other end of that bulkhead? What kind of tank do you have?

Mine didn't look like your outside setup. Mine only has some slits in a plate that i can remove to clean behind. It has to empty at the top somewhere, but I've never gotten behind it to see where the output actually is located. The suction is extremely mild on it, though. I don't know if that would be considered a venturi setup where the water flow over the top creates the suction below... kind of like how those python vacuums function during water change.

 

[ca1ore]

My overflow has a suction type inlet towers the bottom as well. It pulls in water/debri from the water column below the surface.

Mine actually pulls in the a small, thin compartment that then outputs somewhere higher on the inside of the overflow... I've never actually gone digging in there to find out where, though. But it had to do this otherwise the entire tank would drain into your sump when you turned off the return pump.

Yup!! Many tank overflows have this. Marineland for example. Not sure how well it really works, but ......

 

[Saltyanimals]

Yup!! Many tank overflows have this. Marineland for example. Not sure how well it really works, but ......

So another unsolved mystery... =)

I'll update this thread of I ever get a chance to dig back there and take a closer look.

 

[Tastee]

My AIO quarantine tank has this system also. The right hand section of the rear sump is the drain and it has one drain bulkhead at the bottom and another at the top. As others have said it is designed to draw most (or all if your normal water level is < the top drain) from the bottom of the tank.

 

[Saltyanimals]

OK. Confirmed that I eventually saw stuff getting sucked into this lower drain. Had a bunch of nori debris that got sucked into this magical blackhole. The nori was actually a larger piece so now I'm wondering where it goes.. and what else is there now that may be rotting away since I'm not seeing it in my sock. Very interesting.. and a bonus for those that are running UVs for parasite mgmt being able to draw in free floating protomont stage that tends to settle in the lower half of the tank. win win