Going to drill dual drains and returns on 75g. Would Mag 12/18 be enough? Too much?

[Little Reefer Boy]

Hello everyone!

Still in the process of moving up from my 29g to a 75g. I just need to find more time! Since I have it dry, I have the opportunity to setup everything now.

Please let me know what you think, and add any advice as to what I should change.

I plan on drilling two 1" drains and having dual corner overflows, for backup. I also am thinking about drilling the returns as well. Most predrilled tanks have 3/4" returns. Should I put in two 3/4" returns, one for each corner? Or should I make them 1" as well to cut down on head losses?

I would like to plumb the returns as in Fig. B. Would that significantly increase the backpressure though, having to go up the tank height for two returns? I would prefer not to have so much plumbing above the tank as in Fig. A, but would that be a better solution as far as decreased head loss? When you plumb the return as in Fig. A, does the first exit have higher flow?

Also, I think I am going to use a Mag for the pump. It seems like many of you here use the Mag 12 for this size tank. However, if I am going to have dual overflows and possibly dual returns, would I need to step up to a Mag 18/24? I really do like the price/performance balance of this pump line. BTW, the sump will be in the stand.

Thanks so much for any info.

[rcassidy]

Little Reefer,

I have the same setup on a 90gal. I use two 1" drains drilled in the top back corners of the tank, and I have two 3/4" returns powered by a mag12. There are no problems with the drains handling the water flow and I'm considering replacing the Mag12 with a Mag18 (same connections and no replumbing needed) for a little extra power.

Ryan

[BALKER]

I'm using a mag18 for my return with about a 4 foot head on a 70 gallon corner tank and I think the current is nice.

[Little Reefer Boy]

Should I split the returns underneath the tank, then up both corner overflows as in Fig.B? I prefer this way so I don't have to have plumbing running up the back of the tank.

Or should I have the return go up one overflow, then split above the tank as in Fig. A?

I assume I will be fighting less head pressure plumbing as in Fig. A, but if I go with a Mag 18 I should still be alright?

Also, the holes are not yet drilled. That's why I was wondering if I should just go ahead and make them 1" now, for less head loss, instead of the standard 3/4". Good idea?

[BALKER]

I think the head pressure will be the same as the final result of exit is the same in both diagrams. I would go for the cleaner install if it were me. I will say that I had to add cap 900 behind rock work to keep debris from building underneath my then my tank is 3 feet deep also.

[Little Reefer Boy]

cap 900? what is that?

[BALKER]

I was told it was decent power head when I purchased it but to be honest it looks like a generic RIO3100. I will replace it soon.

[alphazone]

As far as the return I would do it like A. This is how I have it on my 75g (only single 1" drain though). I get 11x turnover with a Sen 12000 return pump. I get very even flow to both outlets. No need to do it like in B, though I do use generous 3/4" plumbing to reduce restriction around all the bends.

[Little Reefer Boy]

Would a Mag 18 be too much flow for a 75g? I was leaning towards this over a Mag 12 in case I wanted to split off the return more later. If it was too much flow at first, I could always split some flow back to sump.

[rcassidy]

Couple observations with both designs. Sorry I didn't comment earlier....

Design 1.
If you do it this way you will have to put a ball/gate valve on each of the outputs to adjust the flow. Otherwise one will output will flow a lot more than the other. The other will most likely get minimal current.

Design 2
Design 2 gives you more head loss with the addition of more elbows. Less efficent, less turn over.

If I were you, I would try and run the main supply up the center of the tank, "t" it in the middle and run to each side. This gives you the benefit of having less elbows than design one, and even water pressure out of both returns. That way you won't have to use valves on each end to control the output.

Hope this helps
Ryan