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75 gallon tank

Overflow - 700 GPH, 1500 GPH or something else

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5 Comments
by
blakew
, 01-28-2012 at 01:36 AM (2771 Views)
I'm ready to order the overflow but wanted to get some input from some of you guys with more experience. After all I'm really liking the idea provided in one of my earlier blogs about using an MP-40 and maybe adding an MP-10 for flow over my planned use of a snapper hybrid (less electrical use and fewer holes in the tank). I've also just about talked myself into the AI Sol leds because they're more electrically efficient and if they last as long as advertised will be a significant savings in buying bulbs.

So my plan for drains and returns was to use a 700 gph overflow with a wye. One side stays 1 1/2" and goes to the skimmer section on the right side of my sump. The other side reduces to 1" with a ball valve to control the amount of flow and goes to the cheato area on the left side of the sump. Both of these overflow into the middle section where my return pump, heater, charcoal reactor and biopellet reactor are located. The return pump would be a Mag 7 (with the head this wouldn't over power the 700 gph overflow).

Then, based on Marc's manifold design on his 400, I got to thinking I could upsize the return pump and feed both the charcoal and biopellet reactors as well as the return from the same pump, saving myself a pump to feed the two reactors. I was thinking if I did a Mag 12 the manifold could feed both reactors and have a ball valve controlled bleed off back into the skimmer area to keep the flow to the return from over powering the 700 gph overflow box. My concern is if something blocks the overflow or drain line the Mag 12 even dialed back as described above could over power the drain.

So my first question is should I go with the 1500 gph overflow (provides redundancy but adds another hole to the tank) or do two drains provide twice the opportunity for something to go wrong? Next question, see anything in my revised return pump planning you'd change?

Any and all thoughts are welcome.

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‎ Tank Entry , ‎ Plumbing , ‎ Questions - Need some input , ‎ Equipment

Comments

  1. blakew's Avatar
    I may have to rename the blog...I've been measuring the tank and depending on where I measure, the tank could be a 75 or a 90. If manufacturers use the outside dimensions of the trim the tank measures 48.5" x 18.5" x 23" @ 7.48 gallons per cubic foot that's 89 gallons...If tank manufacturers use the inside dimensions, the tank measures 47.25" x 17.25" x 22" @ 7.48 gallons per cubic foot that's 77 gallons.

    I don't know what the tank manufacturer called the tank, but I'm going to call it a 75 based on the inside dimensions, although once I get sand and rock in there it'll actually have less than 75 gallons in it.
  2. Midnight's Avatar
    Either way 90 or 75, you will be better off with two than one. I would suggest you use two 1in drains or bigger, I don't know what your options are. Drains are are safer and in my opinion easier to silence the bigger they are. If you are doing two glassholes overflows I would do the 1 1/2 in ones and tie them together a few inches below the holes. Mag 12 should do the trick, but you will have to plumb it efficiently.
  3. blakew's Avatar
    I was planning to use the glass-holes kit. I only want to flow 5x the tank volume (400 gph+/-) through the sump. At 5'+/- head back into the tank, the Mag 12 will flow around 1100 gph. Bulk Reef Supply recommends using a Mag 3 (350 gph+/-) for their biopellet reactor and I'm figuring around the same for the charcoal reactor (maybe less). A Mag 7 would work for the return to be between 3x & 5x tank volume, and uses 70 watts of electricity. A single Mag 3 could power both reactors at an electricity use of 37 watts. The Mag 12 will do the job at 110 watts of electricity.
  4. Midnight's Avatar
    you also have to account for tee's and elbows, for head pressure
  5. blakew's Avatar
    Yes, minor losses aren't so minor in a system like the one described.

    So let's start with the desired flow at the highest point in the system. I want approximately 5x the display tank's volume through the sump. 78 gallons x 5 = 390 GPH at the return. There's about 6 feet of 1 1/2" pipe (twice the size of the output on the Mag 12), a 1 1/2" union @ 7 LF equivalent length of 1 1/2" pipe, a 1 1/2" Tee (flow side) @ 1.5 LF equivalent length of 1 1/2" pipe, and (3) 90 degree bends @ 2.4 LF equivalent length of 1 1/2" pipe each. So the hydraulic total length of 1 1/2" pipe is approximately 22 LF. If I want approximately 400 GPH through this 22 LF of pipe I'm going to have approximately 0.4 feet of head loss. So 0.4 feet head loss plus the 5 feet of lift reduces the 1200 GPH out put from the pump to 1035 GPH.

    So now I have 635 GPH flow to push through the reactors and back into the sump.

    I've already accounted for the lift to get to the tee at the manifold so I don't need to account for it again. The manifold is about 1.5 total of 1 1/2" pipe, a 1 1/2" tee (branch side) @ 5.2 LF equivalent length, another 1 1/2" tee both flow side and branch side @ 8.0 LF equivalent length, (2) ball valves @ 1.0 LF equivalent length each, and a reducer/hose barb @ 10 LF equivalent length. So the hydraulic total length of 1 1/2" pipe is approximately 27 LF. Using 600 GPH through this 27 LF of pipe I'll have approximately 0.7ish feet of head loss.

    Now we have to do several itterations to determine the total available flow. 5.5 feet of head loss for the return into the tank and 0.7 feet of head loss in the manifold equals a total head loss of 6.2 feet. @ 6 feet of head the Mag 12 can deliver 950. I want 400 into the tank so that leaves 550 through the manifold. The head loss for 27 LF of 1 1/2" pipe with 550 GPH is about 0.6 feet. Which is close enough to the 0.7 feet used for the first itteration so I'll call it close enough.

    I understand that this is an approximation and it could be dialed in much closer but with these calculations, I can get 400 GPH turnover through the display, feed the reactors with 350 GPH and still have 200 GPH running into the cheato section. With that both 1 1/2" overflow pipes can run straight down into the skimmer section.

    Anyway that's what I was thinking. Hopefully if anyone reads this, they can see Midnight's point that "minor losses" should be considered rather than just vertical head like I emplied in my earlier response.

    Thanks again Midnight, with your help and making me look at all the angles maybe when I actually get the parts all together the tank will run as desired.

    PS I went ahead and ordered the 1500 GPH overflow today.