Two return pumps, one return - operate in parallel or series?

[Greenjeans]

I'm planning the plumbing for my first tank, 120g display with a 40g sump. The display is drilled for one return, and I intend to use two ReefOctopus Varios-2 pumps as the return.

I was originally planning to run them in parallel (with check valves and the like), but after reading this I'm wondering if it's a better idea to run them in series - http://www.mcnallyinstitute.com/18-html/18-1.htm

Seems like running in series would get me more flow, but the whole point of running two is to handle the case of one failing. In this case, one pump would be also having to move water through the dead pump, and flow would be terrible...?

 

[ccombs]

Parallel IMHO

 

[lakai]

just use one for each of the returns.

 

[Greenjeans]

I only have one return drilled in the tank...hindsight is 20/20

 

[maroun.c]

If u run the parallel u need to have check valves so if one dies water continue to flow to the tank from the second pump and not flow out through the dead pump. I run two pumpsmin series but just to increase head performance. Yes if one does second pump will continue to push water through it

 

[Greenjeans]

Yeah, I planned to have check valves after each pump if ran in parallel.

Seems like the consensus is to run two pumps in parallel, despite the head loss, for better flow if one dies?

The alternative is to run them in series, which will provide better flow, but very low flow if one dies.

Given that I'll be using an apex for control and monitoring, I very seriously doubt the system will ever be running with a dead return pump for very long at all (I have a spare on hand). I'm sorta leaning towards running in series...these two varios-2 pumps aren't that big, and I will be running a large refugium on my 160g system.