Dual drains in overflow, vertical vs side by side?

[David R]

A picture tells a thousand words, even if it's a crappy MSPaint one...



The tank I'm setting up will be on a low stand and the sump plumbed thru the wall in the garage on the other side. The top of the tank is only going to be 1300mm high and the top of the sump about 900 high, so it doesn't give me much fall on the drains. I'm planning on two 50mm drains and running a Laguna max-flo 2900 pump pushing ~2500GPH at ~1000mm head. I'm thinking of putting the two drains one above the other so the lower one can/will operate as a full siphon (A), but if I do that the lower one will only have ~100mm fall after a horizontal run of 2-300mm. If I have them side by side (B) the fall will increase to around 200mm after a similar horizontal run for both drains. I've had a look at CHOPMERS sticky in the DIY forum on pipe flow rates and with a 36" fall a 50mm drain should flow 2400GPH, so two 50mm drains should be well capable of handling the flow from the pump. However, the amount they flow will be reduced because of the lack of vertical fall; how much, who knows?

So Option A, over-under with the bottom one running at a full siphon, or Option B, side-by-side with more vertical fall?

 

[KAWAMIKIE]

Either way should work fine. Look up Durso or Bean Animal stand pipes to reduce noise in your over flow. You can tee your return in the event you need to throttle back the flow.

 

[David R]

Yeah I'm familiar with durso and the bean animal system, I was kinda thinking the option A would work like a bean animal set up though may need a ball valve on the lower drain to set the siphon. Its a bit of an unusual set up in that there isn't much fall from the drains to the sump, I'm really just wondering how that will affect the flow of the drains.

 

[guano]

I think option B would be loud. It may start sucking air and get that dreaded flushing toilet sound. I like option A with a ball valve on the lower drain. Can't really comment on the flow with such a shallow drop. The only thing I can think of that it may effect will be how fast it will create a siphon back when you cut power the pump.

 

[Apexden]

i think that a would not work, maybe? the bottom drain would take on most of the water and the top would just trickle ever so slowly. it would work but not so much, kind of a back up drain.

 

[Apexden]

MY BAD, i reread the post i was thinking it was one on top of each other

 

[duanes]

I have had a sump not more than 10 inches (25 cm) below the main tank. The short fall really had no effect on the velocity, it has to do with the gph produced by the pump.
And I actually think an additional drain above the main drain is a good idea as insurance against the main drain getting plugged by plant debris, a dead fish or whatever.

 

[pk705]

I would go with plan A and try to run it beananimal style. I don't think the horizontal piping would impact it much, as horizontal piping going to vertical is mostly going to have a similar effect as vertical piping going to horizontal. Sloping the pipes ever so slightly might help a minimal bit (especially with eliminating trickle noise in the upper one). Good luck.

 

[David R]

Thanks, Option A it is, I'll see how it goes as-is and add a ball valve if needed.