Bean Animal - 1.5'' drains vs 2'' full siphon drain - 600-gallon tank

[yellrihs]

Hi All,

In the final stages of building out a 600-gallon peninsula. Planning on running two Ecotech Marine L2's as the returns.

Need some advice on external overflow plumbing/bulk heads sizes for a Bean Animal setup. 1.5" full siphon with duel 1" returns (One for each pump) or a 2" full siphon with duel 1.5" returns.

3 bulk head holes will be drilled in the overflow, just torn between 1.5" vs 2" for the full siphon.

I currently run one Ecotech Marine L2 on my 350-gallon with 1.5" full siphon (bean animal), just now sure if it would handle two or if I should bump up to 2" full sypon on the new build (600 gallon) with two L2's.

Thanks!

 

[SPR1968]

I can’t help with the question, but I can bump the thread to see if we can get you some assistance.

 

[DCR]

A 1-1/2" full siphon will be plenty for two L2's with 1" returns. The 1" returns will limit the flow of that system. I would expect about 500-600 gph from each. If you went with dual 1-1/2" returns, then I would go with a 2" full siphon. That system could probably handle 2500-3000 gph, but the overflow box then likely becomes the limiting factor. I would think you would need at least 60-72" of overflow weir to support that much flow. I think the flow ratings on most overflow boxes are overstated.

 

[Ben Pedersen]

A 1-1/2" full siphon will be plenty for two L2's with 1" returns. The 1" returns will limit the flow of that system. I would expect about 500-600 gph from each. If you went with dual 1-1/2" returns, then I would go with a 2" full siphon. That system could probably handle 2500-3000 gph, but the overflow box then likely becomes the limiting factor. I would think you would need at least 60-72" of overflow weir to support that much flow. I think the flow ratings on most overflow boxes are overstated.

This comment confuses me. Per the Ecotech L2 documentation, the return pipe for an L2 is only 1.25”. In your response, you say if you increased the return to 1.5” the L2 would push more water. Why would you use a bigger size the the max size of the pump return, and why would this move more water?

Vectra L2 Spec:
Flow: 3,100 gph (11,500 lph)
Wireless: Included
Max Head Pressure: 21.5 feet (6.5m)
Footprint: 5 in. x 8.5 in. (126.8mm x 215.15mm)
Fittings: Input: 1.5 in. (38 mm) Output: 1.25 in (31.75mm)

 

[Dread Pirate Dave]

My understanding is that the larger return pipe diameter results in less head pressure loss. (so more flow)

 

[DCR]

Pumps are generally designed with relatively small discharge nozzles for improved pump efficiency. One should not assume that using the same size pipe as the discharge nozzle is the correct choice. Larger pipe sizes will always deliver more flow due to lower fluid velocity and friction loss. The frictional loss goes up with the square of the velocity, so the head loss escalates rapidly. Pipe size selection in the engineering world is generally an economic compromise between installed cost (larger pipe and valves) and operating cost (higher head pump and more power consumption). I would expect that you would probably get 800-1000 gph of flow using 1.25" return piping with an L2 in a typical aquarium installation. You could probably increase that to about 1200-1500 gph with 1.5". This is just based on my typical rules of thumb for economic pipe size selection.