Two return pumps, one return - run them in parallel or series

[CapnGreenJeans]

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 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 since one pump will have to also move water through the dead one.

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.

 

[Michael Hoaster]

I took a look at that article. It makes some interesting points. I still think I'd go parallel, so you have two returns going into the display, giving you more water movement options.

Still, in series is intriguing. If you decide to go that way, let us know how it goes!

 

[CapnGreenJeans]

Like I mentioned, my tank is drilled for only one return, limiting my options - both pumps need to feed into the same pipe somehow

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[Michael Hoaster]

That makes sense. Returns don't have to run up through the tank of course, but I guess you don't want to do that.

 

[CapnGreenJeans]

Yeah, I want both pumps to add flow and turnover to the display

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[CapnGreenJeans]

I guess I could do something like this to create a second return if I wanted to go that route

https://gmacreef.com/wp-content/uploads/2013/07/return-line-mount-tank-trim.jpg

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[Sk8r]

There are easier ways to get flow into a tank: a wavemaker of one sort or another. I've not seen a two pump tank and have a few questions. When a pump stops, the gravity flow of the tank delivers a certain amount (set by an inner wall in the downflow box) to the sump, and the sump level rises. If you have one of two pumps stop, but not the other, the surviving pump is going to continue to pump water up FROM the sump, and water will keep falling down. If the two pumps are balanced, I suppose that it would be like having your single pump lose a great deal of its power, so the tank functions, but slowly and weakly. I don't see that it would be a question of overflow.

Usually, however, you just have one potent pump driving both returns, connected by a Y. You lose some force, but you get the directionality. And if the pump stops, it stops and the tank drains to a set level.

I have a single return, but I use a Maxspect Gyre, which does a rolling flow from top to under-rockwork and throughout the tank. Look up 'wavemaker' and check those out.

 

[CapnGreenJeans]

I've got flow within the tank taken care of with Vortech pumps.
This is specifically to address tank/sump turnover flow.

I think you're confusing return plumbing and overflow plumbing.

Dual pumps are used for redundancy - if (when) one fails my tank will still have circulation with my sump until the problem pump can be fixed.

Each pump will feed through a check-valve, to prevent backflow if one dies.

 

[jerseyboy]

this may seem dumb but why not drill a second hole and use one larger pump then split the return. im doing this on a 135 gal and it works fine

 

[CapnGreenJeans]

That is an idea, but makes me nervous - this is a CustomAquariums build that is too far along in the construction process to change the drilling, and drilling it myself sounds terrifying on a tank this expensive.

I think I'll plan for a HOB return, something like this https://www.customaquariums.com/1-2...h-barbed-elbow-for-non-drilled-aquariums.html

and then run each pump to its own return.

Hopefully I can hide the additional plumbing so the return doesn't look too out of place

 

[Sk8r]

For your peace of mind, a reasonably (not over-) stocked tank can easily go 8 hours without circulation in a power-out. There is also a pump made by Penn-plax that can (from a shielded spot in your rockwork, provide battery-powered bubbler-circulation if the power goes out. This can run as long as you feed it batteries, and even the bubble output of one small diffuser is sufficient to aerate a 100 gallon tank.
In a power-out situation, of course, even if you have 2 regular pumps, you have no pumps.

Be SURE that the sump has enough free room to take the draindown from TWO downflow boxes at once in a power-out.

And that your skimmer, at low-water level in the sump, has enough water depth to work properly at normal times.

 

[Daniel Black]

I had the idea of making a double pump with one of these pumps. I've seen something similar used to brew beer. Do you think you can work with that or is that a bad idea?

 

[CapnGreenJeans]

I don't follow what you mean...turn one of those pumps into a "double pump"? How would you do that?

These pumps seem purpose built for recirculating hot water, it might be wiser to use a pump purpose built for our applications?

They all output much less flow than I need, I'm aiming for 20-25 gallons per minute.

At any rate, I already have the 2 ReefOctopus Various-2 pumps.

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[CapnGreenJeans]

I went ahead and ordered one of these https://www.customaquariums.com/3-4...h-barbed-elbow-for-non-drilled-aquariums.html

I'll plan my plumbing to have two return pumps, each hooked to their own return - one return will be HoB, the other will be drilled...hopefully I can make that look nice and clean.

Anyone have any good pictures of dual pump/dual return plumbing? I need to start mapping this out. How would you set up a manifold for future gear - branched off of one of the returns, or a small manifold on each?