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  1. #1

    Which return pump

    Hi all, just getting the equipment together now as landscaping is done. So, I want to produce a true 18000 ltrs per hour with the return pump, question is which one and is variable better. So, we are returning from a 4" bottom drain and a 4" skimmer line into a combi drum/ bio filter that can have a flow through it of up to 30,000 ltr per hour, then through a UV which is recommended maximum at 20,000 ltrs per hour and return to pond is 2". I would say the journey for the water from the bottom drain to the combi drum/ bio chamber is about 4 meters with 5 swept 90 deg bends and the return distance is the same, with the same amount of bends. I am aware that, if I buy a 20000 ltr per hour pump, I am likley to lose up to 50% water volume through the distance and bends, to 10,000 ltr per hour, which is no good, so do I buy a 30000 ltr per hour and hope its no too much, or a 30,000 ltr/ hour variable pump. Help please would be much appreciated. Thanks



  2. #2
    Buy the 30k variable and turn it down if you need to.


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  3. #3
    That's what I was initially thinking, but if I loose 50% through bends and distance etc, at 30000 ltrs/hour I would only be getting 15000 ltrs per hour, or would a 30000 ltr per hour do 18000 ltrs per hour over that distance easily? If so, which pump would you recommend?

  4. #4
    Difficult really, I’d be tempted by something with a bit of backbone rather than a cheapy Chinese one.
    I can recommend Auga as I have 2 and they’re real beasts but not cheap.
    Quality product, they’re 3 times heavier than my cheapy one from coastal koi although that’s been fine so far to be fair.
    If you want serious flow, low energy but high price then flowfriend without question.
    You could run two normal ponds off one of those bad boys.
    They’re the only pumps I have personal experience of, others may be able to recommend a decent alternative.


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  5. #5
    Senior Member Rank = Supreme Champion davethefish1's Avatar
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    what diameter is the UV?
    they can restrict a lot.
    you may need to put a bypass and split the flow around the UV the get actual 18,000lph

    nothing in life is certain least of all pump return calculations
    so you could try a single 30,000 vario and see how it goes, or 2 x 20,000 vario's and have redundancy...

  6. #6
    UV is an Evo Aqua 110v, so 2" pipe work for UV. I only have 1 x 2" return so have to do it with one pump

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  8. #7
    Senior Member Rank = Supreme Champion davethefish1's Avatar
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    Quote Originally Posted by Mabbs View Post
    UV is an Evo Aqua 110v, so 2" pipe work for UV. I only have 1 x 2" return so have to do it with one pump
    if it's this unit (below) the offset manifolds, of which there are 4...
    look like they will create quite a lot of turbulence and therefore restriction.
    do you actually need 18,000 lph across them?

    Which return pump-3539-jpg

    just my opinion
    but i'd make a bypass and feed half the flow around them.
    i wish i'd done it with mine...
    i've got a 30w evo aqua uv with 1 1/2" connections and a maximum flowrate of 15,000 lph.

    Which return pump-0002292_evolution-aqua-evo-30w-uv-unit_550-a

    but it creates quite a bit of restriction.
    i'm pushing 7,000 lph actual through with a 20,000 vario at 80%...no where near 15,000 lph...
    Attached Images Attached Images
    Last edited by davethefish1; 06-06-2020 at 11:54 PM.

  9. #8
    Extreme Koi Member Rank = Adult Champion NickK-UK's Avatar
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    Quote Originally Posted by Mabbs View Post
    Hi all, just getting the equipment together now as landscaping is done. So, I want to produce a true 18000 ltrs per hour with the return pump, question is which one and is variable better. So, we are returning from a 4" bottom drain and a 4" skimmer line into a combi drum/ bio filter that can have a flow through it of up to 30,000 ltr per hour, then through a UV which is recommended maximum at 20,000 ltrs per hour and return to pond is 2". I would say the journey for the water from the bottom drain to the combi drum/ bio chamber is about 4 meters with 5 swept 90 deg bends and the return distance is the same, with the same amount of bends. I am aware that, if I buy a 20000 ltr per hour pump, I am likley to lose up to 50% water volume through the distance and bends, to 10,000 ltr per hour, which is no good, so do I buy a 30000 ltr per hour and hope its no too much, or a 30,000 ltr/ hour variable pump. Help please would be much appreciated. Thanks
    Yikes - poor pump. Probably worth looking at the maximum back pressure operating range that the pump can survive otherwise you're going to be burning out pumps or reducing their operational lives.

    The 20K (190W) and 30K (450W) have the same max head height (5.5m) and the same 2" connectors. So why does it consume over two times the power for 50% increase in flow rate? The non linear need for more pressure for flow rate for 2".

    I stole this from another thread and originally from a website in US gallons, indicating the rough ideal max throughput - however at 20psi is a pump with a 14 meter head for reference. The estimate is a linear scaling so not entirely accurate:
    Screenshot 2020-06-07 at 06.12.05.png

    So to get your 30,000 lph through 2":
    a) you'd need 20+psi capable pipe and fittings
    b) you'd need a pump capable of running a 100% duty cycle of 14 meter head plus the back pressure..

    So 5.5m is 7.8 PSI. Scaling above that's 14,360 lph so clearly I'd take either the Varipump or the website data with a pinch of salt (I suspect the varipump does more PSI but they don't want the burnt out returns).

    Anyway ... back to my point as the above is assumption based on assumption based on manufacturer marketing..

    The concern I have is that with the 30,000lph pump you'll be (a) constrained by the 5.5m back pressure max and (b) you'll not get 30,000lph through it as you'd need a system capable of 30,000lph through 2" pipe with the bends which I don't think the varipump would give you (assuming high pressure pipe was laid?). Eitherway you will be putting a large amount of electricity bill in achieving it. It may be cheaper to relay a larger pipe or have a second 2" return (although two 2" has less pipe area than one 4").

  10. #9

  11. #10
    Extreme Koi Member Rank = Adult Champion NickK-UK's Avatar
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    Quote Originally Posted by RipleyRich View Post
    2" 4m, 5 90s and 36m3 through it: 0.35bar back pressure (3.5m).

    Unfortunately EA don't publish flow-head curves for their Varipumps.. #nothingtohidehonest

  12. #11
    The combi drum also has a 40 watt amalgam built in, so maybe just a bypass. The evo110's data just says it can have 20000 ltrs per hour running through it, so as I only need 18000 ltrs per hour thought this would be OK.

  13. #12
    Quote Originally Posted by NickK-UK View Post
    Yikes - poor pump. Probably worth looking at the maximum back pressure operating range that the pump can survive otherwise you're going to be burning out pumps or reducing their operational lives.

    The 20K (190W) and 30K (450W) have the same max head height (5.5m) and the same 2" connectors. So why does it consume over two times the power for 50% increase in flow rate? The non linear need for more pressure for flow rate for 2".

    I stole this from another thread and originally from a website in US gallons, indicating the rough ideal max throughput - however at 20psi is a pump with a 14 meter head for reference. The estimate is a linear scaling so not entirely accurate:
    Screenshot 2020-06-07 at 06.12.05.png

    So to get your 30,000 lph through 2":
    a) you'd need 20+psi capable pipe and fittings
    b) you'd need a pump capable of running a 100% duty cycle of 14 meter head plus the back pressure..

    So 5.5m is 7.8 PSI. Scaling above that's 14,360 lph so clearly I'd take either the Varipump or the website data with a pinch of salt (I suspect the varipump does more PSI but they don't want the burnt out returns).

    Anyway ... back to my point as the above is assumption based on assumption based on manufacturer marketing..

    The concern I have is that with the 30,000lph pump you'll be (a) constrained by the 5.5m back pressure max and (b) you'll not get 30,000lph through it as you'd need a system capable of 30,000lph through 2" pipe with the bends which I don't think the varipump would give you (assuming high pressure pipe was laid?). Eitherway you will be putting a large amount of electricity bill in achieving it. It may be cheaper to relay a larger pipe or have a second 2" return (although two 2" has less pipe area than one 4").
    OK that's great information. Yes high pressure pipe was laid. Everything is in now, and concreted in. To run more pipe work would be a bit of a nightmare. There are high pressure pumps on the market that are variable, such as the badu, which due to there design have a low energy consumption. Would this be a route to go?

  14. #13
    Extreme Koi Member Rank = Adult Champion NickK-UK's Avatar
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    Quote Originally Posted by Mabbs View Post
    OK that's great information. Yes high pressure pipe was laid. Everything is in now, and concreted in. To run more pipe work would be a bit of a nightmare. There are high pressure pumps on the market that are variable, such as the badu, which due to there design have a low energy consumption. Would this be a route to go?
    I had a look at their SPECT ECO - they're still in the 750W area as a swimming pool pump. Looking at your original post "18000 ltrs per hour with the return pump," so that's doable as a flow rate but I don't have the real world experience on higher pressure pumps - I have the 20,000lph varipump. The reason I was crunching numbers was part of my own design - in the end I settled on multiple 2" returns from the pump pretty much at the same head height as the inlet for the pump with it's longest run being about 2 meters.

    I did note that the SPECT ECO has a 2" inlet and a 1.5 outlet!

 

 

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