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[robs.mark]

Hey all,

I have an odd question. I’m in the process of putting together a new peninsula (72” x 34” x 26”) and have had a new custom tank made with external overflow box. The overflow is a bean Animal with 1 1/2” drains, but I’m now considering making the tank a closed loop to overcome potential flow issues at the viewing end. I have a spare Vectra L2 which I could use, and was considering having just one hole drilled the the base of the tank (not tempered) and using the spare drain for the bean animal for a feed to the L2 - with a random flow program, would this work or would it just mess with the level in the overflow box? I know it’s a little tricky buy I only have one shot to get this right and this ‘hidden’ feed would look better athletically. I’m thinking that because the tank throughput the very low wouldn’t change the active level wouldn’t change either if that makes sense?

 

[KrisReef]

If the open drain is feeding the V2, if the pump stops you must rely on check valves to prevent the tank from draining back through the return. Balancing the flow between return and overflow would be very tricky, but you might get it balanced at slow speeds.

I would not put a hole in the bottom of a tank for a return. It's not a risk that I would want to live with.

Maybe someone else has a solution that will work for you?

 

[KStatefan]

That would be a lot of flow thru the overflow to have all the closed loop flow also. The water level in the tank would also change with the random flow of the closed loop pump. How much would depend on the flow and how big the overflow is. If I was doing a closed loop I would not do it that way.

 

[ca1ore]

IMO, a very bad idea to have any penetrations low down in the tank, for obvious reasons I’d think. What happens when there’s the inevitable bulkhead problem that is ‘open’ to the full tank volume. Asking for trouble and an unforced error. I ran a closed loop in my last tank and it worked really well but the suction and return holes were all at the top of the back panel. Failure would have made a mess certainly, but it wouldn’t have drained the tank.

On the other hand, using one of the bean drains in the external box to feed a closed loop ought to work fine as long as you don’t exceed the capacity of the internal skim box. You’ll also have to configure it so it doesn’t suck air.

 

[robs.mark]

IMO, a very bad idea to have any penetrations low down in the tank, for obvious reasons I’d think. What happens when there’s the inevitable bulkhead problem that is ‘open’ to the full tank volume. Asking for trouble and an unforced error. I ran a closed loop in my last tank and it worked really well but the suction and return holes were all at the top of the back panel. Failure would have made a mess certainly, but it wouldn’t have drained the tank.

On the other hand, using one of the bean drains in the external box to feed a closed loop ought to work fine as long as you don’t exceed the capacity of the internal skim box. You’ll also have to configure it so it doesn’t suck air.

Thanks, Plenty of tanks over the years have had success with closed loop returns through the base of the tank. A good quality BH fitting installed correctly shouldnt be a problem. David Saxbys tank is set up exactly this way, even Jake Adams did this in one of his last videos.

 

[ScottD]

My thought on this is even if you can, should you? Others can probably chime in better on this, but if the idea of an overflow is to get everything out of the tank and into your sump to filter, then sending it right back out into the tank as part of a closed loop defeats that purpose in my mind.

 

[cilyjr]

I've no idea the volume of the overflow but I think you could have many potential issues balancing a syphon overflow as the CL pump ramps up and down. As water level changes you could get lots of splashing and "toilet flushing" as the water level drops.

Also you have the potential to overwhelm the weir if it is a small box.

I get why with a peninsula build, you want to use a cl but seems like a lot of work for 3k gph.

If the tank has rim, I've seen some pretty clever over the top returns that got extended to the far side of the tank.