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Return flow help

Discussion in 'General Discussion' started by nlandgraf, Mar 22, 2019.

  1. nlandgraf

    nlandgraf

    184
    Ratings:
    +2 / 0 / -0
    I am setting up my aquarium again after being down for a few years. With the move I redesigned my plumbing and sump setup, and purchased a new return pump rated at a max flow of 3,645 gph. My overflow is setup as a dual herbie; drains are 1" bulkhead and 1" pipe. For a return off of the pump I am using a 1 1/4" return pipe that T's into 2 1" pipes, and each of those T into another 2 3/4" pipes over the back of the tank (4 3/4" returns in the tank total).

    I was expecting to dial the pump back quite a bit (maybe to 60-65%), but I am running it at dang near full power. My surprise is that my valves on each of my 1" drains are approximately only halfway open; so I am guessing I am probably only moving 800-900 gph with the pump at max power. My intent was to be turning over somewhere between 1500-1800gph in the tank, and also be able to direct some flow over to a manifold. Right now I have the manifold off.

    Is there something that I am missing or not considering that is impacting the amount of water I am moving? I can take pictures when I get home if that helps.
     
  2. aussie Well-Known ReefKeeper Board of Directors Leadership Team GIRS Member

    651
    Cedar Rapids, IA
    Ratings:
    +161 / 1 / -0
    Ever bend intersection and ft of high drops the overal movement of water not sure of your tank but two 45 deg angles has less restriction than a 90
     
  3. Easy E Novice Reefkeeper GIRS Member

    78
    Shellsburg, IA
    Ratings:
    +24 / 0 / -0
    I'm certainly no expert on plumbing, but I think gravity is your enemy here. If the 1 1/4" and 2 - 1" return pipes are vertical and of significant length, there's going to be a lot of water weight in them that's pushing back against your pump. I would decrease the size of the vertical pipe or pipes if I was you. Smaller return lines will allow your pump to move more water not less.
     
  4. nrenn GIRS Member

    257
    Waverly, Iowa
    Ratings:
    +16 / 0 / -0
    That isn't true. Pipe diameter has no impact on head pressure, which is purely a factor of height, ie a 1/2" line with 10 ft of head has the same amount of pressure at the bottom as a 3" line. Additionally, smaller lines will have greater flow restriction than larger due to turbulence effects. You may be thinking of velocity instead, smaller lines will result in higher outlet speeds, but smaller volume.
     
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  5. Derek

    127
    Cedar Rapids
    Ratings:
    +24 / 0 / -0
    This is what I was going to say. The smaller diameter tubing you use, the less volume you will get due to friction loss. Usually a pump that size will tell you a recommended pipe diameter to use and give you a GPH at each diameter. Here's a good chart to start with.

    upload_2019-3-26_7-10-54.png
     
  6. Easy E Novice Reefkeeper GIRS Member

    78
    Shellsburg, IA
    Ratings:
    +24 / 0 / -0
    Interesting. Thank you for clearing that up. Like I said, I'm no expert, but at least I'm a little smarter now.:)
     
  7. nrenn GIRS Member

    257
    Waverly, Iowa
    Ratings:
    +16 / 0 / -0
    Back to the OP, my personal opinion is that turnover rate isn't as important as it once was. I think years ago the recommendation was 5x/hr for FW and 10x/hr for reefing. The main reasons being for surface agitation for gas exchange and transporting nutrients and waste to the sump as fast as possible

    I think advances in in-tank powerheads now provide more than enough surface agitation and flow when probably aimed/positioned. Better filtration methods as well as better understanding of tank chemistry and what goes into a tank also address nutrient export/balance. The end effect being that I believe you can go well below 10x/hr turnover without ill effects.

    This is a lot of speculation on my part though, maybe someone else can comment on high vs low sump through-put
     
  8. Drewster

    223
    Cedar Rapids
    Ratings:
    +55 / 0 / -0
    Not too long ago BRS had one of their informative videos on flow and turnover rates. It discussed how a properly/thorough sump and filtration setup is very effective with just 2x system volume turnover per hour. This is possible with higher internal flow, as in up to 100x turn over in the display tank.
     
  9. Derek34 GIRS Member

    158
    Manchester, IA
    Ratings:
    +29 / 0 / -0
    I would definitely say your biggest enemy is the pipe diameter. Bigger pipe = more volume as stated before. I didn't see how far the water is being pumped vertically. As you probably know the more head height there is the less volume you will get. If possible reduce head height.(most likely not possible.) You might try running a larger output pipe from your pump up to the head height you are looking for and then creating your 4 return pipes from there. So put your junctions higher as opposed to lower. This may help to reduce the flow restriction in the multiple smaller pipes on the way up. Also try to use 45's instead of 90's as stated previously also.
     
  10. Drewster

    223
    Cedar Rapids
    Ratings:
    +55 / 0 / -0
    What brand and model pump are you using? Some pumps have high flow/volume ratings but can't handle head pressure well. Knowing the pump you are using and the height from pump to the top of the tank will help in guiding you on this.
    Just curious, what size tank are you setting up?
     
  11. M2R GIRS Member

    16
    Charles City
    Ratings:
    +3 / 0 / -0
    They are all factors in flow rate including diameter, length and height of the tubes. The pump is rated at a particular height. Smaller diameter tubes increases loss to friction, angles also increases losses to friction and create a deceleration and length of tubing also create a loss to friction. If you want to understand it better look up laminar flow and negative acceleration around a curve.
     
  12. Derek

    127
    Cedar Rapids
    Ratings:
    +24 / 0 / -0
    I just found this datasheet online and thought I would add it to this thread as well. It has some more useful information on friction loss in PVC fittings and different corn/angle fittings. You might not be able to decrease the head height from pump to tank, but if you can remove some elbows in your design, you might be able to save some friction loss.

    [​IMG]
     
  13. M2R GIRS Member

    16
    Charles City
    Ratings:
    +3 / 0 / -0
    Most things presented as absolutely necessary, turn over, flow rates, par values, can be disregarded. Water chemistry and experience are 95% of the game. Many a reef keeper expressed shock after spending huge money getting all of the things they were told they needed when they looked at my DIY on the cheap system with a diverse reef with multiple anemones, lps, sps, tridacna all thriving without checking any of the boxes that they were told they absolutely had to check. My favorite was the mixed reef with walmart daylight bulbs with commercial actinic ho bulbs. lol, reef central lost its collective mind looking at that set up and healthy animals. When you have been doing this for decades and long before any of this equipment existed you get a good BS detector for what you absolutely need or don't
     
  14. M2R GIRS Member

    16
    Charles City
    Ratings:
    +3 / 0 / -0
    In short I agree, the high turn over rate is not needed. :)
     
  15. xroads Veteran Reefkeeper Leadership Team GIRS Member

    La Porte City, IA
    Ratings:
    +1,006 / 6 / -0
    I agree also. I would trade turnover for inside the tank flow personally.

    Honestly I would get rid of all the t's and have one return which will increase turnover, and invest in several powerheads.
     
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  16. nlandgraf

    nlandgraf

    184
    Ratings:
    +2 / 0 / -0
    I cut out my return that T's into 4 areas for one 1 1/4" return in the corner of the tank. This also reduced the return by 5 elbows for water to flow through. This barely impacted my flow as I only reduced my DC pump flow by 5% to get flow balanced again without adjusting valves.

    I opened the pump up and there was nothing blocking flow, but there was grinding marks on the inside of the housing.

    My pump also arrived without a power cord. I used a cord I had that matched what the product said, but requested a return to the vendor due to those issues. I also switched to the pump 2 sizes up as it was on sale and only cost $25 more for the upgrade. Crazy how things work out :)
     
  17. Derek34 GIRS Member

    158
    Manchester, IA
    Ratings:
    +29 / 0 / -0
    Sounds like things may be looking up! Glad to hear it! Keep us in the loop and let us know what you think of your new pump once you get it.
     
  18. nlandgraf

    nlandgraf

    184
    Ratings:
    +2 / 0 / -0
    I have been running the upgraded pump for a few weeks now. I am not regretting getting the larger size, and I am further convinced there was an unidentified issue with my last pump. I had a new issue arise in using this larger pump though.

    As I mentioned earlier, I switched from T-ing off into 4 return lines and did a little replumbing to just one 1 1/4" corner return. I dialed the pump down considerably and I still had sand blown off of 1/3 of my tank bottom. I wanted the increased flow for the sump turnover, and instead of replumbing again, I decided to try a different approach.

    My return is 1/2" below the surface of the water, and if I added an elbow I would be too deep and overflow my sump when the pump is off. I didn't want to tear into the plumbing again, so I bought a PVC endcap and took a rotozip to it. I slid the cap on the bottom of the pipe and now have flow directed towards the front of the tank. The best part about using the rotozip is that I made a much larger opening that I cut in than an elbow would have allowed. I am thinking I am going to slip the cap off and drill a hole or two in the bottom to get a little flow directly below.
     

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