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    Thread: Pond spin

    1. #1
      Jacques is offline Senior Member
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      Pond spin

      Most call it "pond spin". There are probably other terms for it too. In short, when the pond water slowly rotates (pond spin) then solids will settle to the center point of the pond (which is hopefully where the bottom drain was installed).

      But how fast should the pond spin? The research I found suggested 6 to 12 inches per second for high-density commercial trout and tilapia farming (measured at the furthest point from the bottom drain). Koi prefer much calmer waters so these number are likely on the high side. I would think around 3" per second is more like it.

      Has anyone stood next the pond with a stopwatch to measure this lately?

    2. #2
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      I guess you'd need a circular pond to see this effect as I've never seen it on my rectangular
      outdoor ponds but did on 10' round tank in the garage. But I don't think I had more than maybe
      1" per second movement on the surface. The one return from the filter was near the bottom of the
      pool and that was with about 800 gallons of water and an ES2500 pump.
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    3. #3
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      I get a lot of current in my 12 foot intex pool. but it is only 1400 and I'm flowing about 4,000gph and have a 40 liter air pump also..i guess I could put a empty water bottle on and see how long it takes.

      i don't have a bottom drain or skimmer just a midwater intake and the bottom is 100% clean all the time

    4. #4
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      The TPR designs that we recommend impart the spin. For single bottom drain systems, the spin is one direction only. For two or more bottom drains the spin is reverse direction around each bottom drain, so that there is no interference from the flow of neighboring bottom drain. I don't know that anyone has posted a spin rate, so don't know how to tell you what the rate should be, but several have ponds with TPR''s that should be able to give you measurements from their ponds.

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    5. #5
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      Quote Originally Posted by icu2 View Post
      I guess you'd need a circular pond to see this effect as I've never seen it on my rectangular
      outdoor ponds but did on 10' round tank in the garage. But I don't think I had more than maybe
      1" per second movement on the surface. The one return from the filter was near the bottom of the
      pool and that was with about 800 gallons of water and an ES2500 pump.
      Thank you for your input Steve. As you know, it is possible to spin a rectangular pond but not as easy as round / oval.

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      Quote Originally Posted by kevin32 View Post
      I get a lot of current in my 12 foot intex pool. but it is only 1400 and I'm flowing about 4,000gph and have a 40 liter air pump also..i guess I could put a empty water bottle on and see how long it takes.

      i don't have a bottom drain or skimmer just a midwater intake and the bottom is 100% clean all the time
      That is a lot of circulation for 1400 gallons! I am guessing you do not have large fish in the intex? Smaller fish cope better with uncomfortably large water velocities.

      If you are returning in 1 x 2" pipe I am guessing your water velocity is about 15 inches per second! Which translates into the water bottle completing one revolution in about 29 seconds. Would be interesting to compare my guess to what you can measure.

    7. #7
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      Quote Originally Posted by RichToyBox View Post
      The TPR designs that we recommend impart the spin. For single bottom drain systems, the spin is one direction only. For two or more bottom drains the spin is reverse direction around each bottom drain, so that there is no interference from the flow of neighboring bottom drain. I don't know that anyone has posted a spin rate, so don't know how to tell you what the rate should be, but several have ponds with TPR''s that should be able to give you measurements from their ponds.
      Cannot agree more about TPRs. I never want a pond without them.

      For those not yet converted, break open a tea bag and drop a few tea leaves in a round salad bowl half full of water. Let the leaves soak up some water for an hour or 2 (so they don't all float). Now gently stir that water with a spoon, remove the spoon and watch the non-floating leaves collect in the center of the bowl. If the bowl was the pond, this is where the bottom drain will now suck in those leaves. Now repeat with a flat-bottomed bowl to proof to yourself that this has nothing to do with the slope of the pond floor around the bottom drain, but instead the magic lies with pond spin and pond geometry.
      Last edited by Jacques; 1 Week Ago at 03:11 AM.

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      To me the elusive balance lies in getting enough spin to clean the pond and distribute O2 but not too much to make the pond an uncomfortable home for the koi (with areas of the pond they avoid or dislike).

    9. #9
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      Quote Originally Posted by Jacques View Post
      That is a lot of circulation for 1400 gallons! I am guessing you do not have large fish in the intex? Smaller fish cope better with uncomfortably large water velocities.

      If you are returning in 1 x 2" pipe I am guessing your water velocity is about 15 inches per second! Which translates into the water bottle completing one revolution in about 29 seconds. Would be interesting to compare my guess to what you can measure.
      I'm curious if you've read that or in your opinion that applies to all ponds or just circular ones?
      --Steve
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      Quote Originally Posted by icu2 View Post
      I'm curious if you've read that or in your opinion that applies to all ponds or just circular ones?
      I once got a temporary setup wrong and the result was high rotation speeds in a small round QT-type pond (similar to kevin32's Intex I would imagine). I saw the fish every day over a 4-month period. Smaller fish (up to about 10" - 12") would frequently swim in the strong current whereas the larger fish looked uncomfortable (staying at the bottom and generally not swimming around as much as I would expect). I also saw this in an elongated pond some time back where the pond was basically a river as a result of a high circulation rate and the pond being very narrow.

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      Did I understand your question Steve?

    12. #12
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      Quote Originally Posted by Jacques View Post
      Did I understand your question Steve?
      Yes. I guess it's just depends on the definition of large velocities. My 4000 gallon
      rectangular pond turnover rate is about 12,000 gph and I haven't seen any problems.
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    13. #13
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      Quote Originally Posted by Jacques View Post
      Cannot agree more about TPRs. I never want a pond without them.

      For those not yet converted, break open a tea bag and drop a few tea leaves in a round salad bowl half full of water. Let the leaves soak up some water for an hour or 2 (so they don't all float). Now gently stir that water with a spoon, remove the spoon and watch the non-floating leaves collect in the center of the bowl. If the bowl was the pond, this is where the bottom drain will now suck in those leaves. Now repeat with a flat-bottomed bowl to proof to yourself that this has nothing to do with the slope of the pond floor around the bottom drain, but instead the magic lies with pond spin and pond geometry.
      Thanks! Now I understand how to read tea leaves.

    14. #14
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      Quote Originally Posted by icu2 View Post
      Yes. I guess it's just depends on the definition of large velocities. My 4000 gallon
      rectangular pond turnover rate is about 12,000 gph and I haven't seen any problems.
      Just to clarify - I am talking currents in the pond and not turnover rates or flow rates in the return lines. With your 12 000 gph returned to the pond, you can create currents in the pond by having say 4 returns spread out along the pond perimeter, each returning 3 000 gph. In a circular pond that will make the entire thing spin. In a rectangular pond, less so.

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      Quote Originally Posted by kdh View Post
      Thanks! Now I understand how to read tea leaves.
      Let me know if you need to understand far-infrared

    16. #16
      coolwon is online now Senior Member
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      Quote Originally Posted by Jacques View Post
      Just to clarify - I am talking currents in the pond and not turnover rates or flow rates in the return lines. With your 12 000 gph returned to the pond, you can create currents in the pond by having say 4 returns spread out along the pond perimeter, each returning 3 000 gph. In a circular pond that will make the entire thing spin. In a rectangular pond, less so.
      Peter Waddington would place the water returns very low down in the pond, about a foot above the pond floor.

      He referred to them as TPR'S, tangential pond returns. Each of the return pipes was built into the pond walls at a tangent.

      The low level returning water would set up the spin motion of the mass of water in time and drive any dirt build up to the bottom drains.

      The current created by the TPR'S was also to exercise and improve the fishes body shape.

      The slowly circulating water would help to shift the surface water dirt towards the pond perimeter for the weir/skimmers with the assistance of the prevailing winds to catch.

      Garfield.
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      Quote Originally Posted by coolwon View Post
      Peter Waddington would place the water returns very low down in the pond, about a foot above the pond floor.

      He referred to them as TPR'S, tangential pond returns. Each of the return pipes was built into the pond walls at a tangent.

      The low level returning water would set up the spin motion of the mass of water in time and drive any dirt build up to the bottom drains.

      The current created by the TPR'S was also to exercise and improve the fishes body shape.

      The slowly circulating water would help to shift the surface water dirt towards the pond perimeter for the weir/skimmers with the assistance of the prevailing winds to catch.

      Garfield.
      I had someone help me with a Computational Fluid Dynamics Model (Garfield: he works for the CSIR in Pretoria) simulating the hydraulics of my one pond. Installing the returns too close to the surface (less than 10" / 250mm deep) resulted in lost momentum and the pond water would move very little compared to the velocity of water coming out the returns. We never looked at returns very close to the pond floor as I was concerned about turbulence so close to the bottom drains.

      Based on research in the US, returns placed under the surface should impart 15% - 20% of their velocity on the pond in the form of pond spin. So if returns flow at 1 meter per second, a round pond should spin at between 0.15 and 0.2 meter per second along the sidewalls (which I believe is too fast for koi). For odd-shaped ponds the 15% - 20% would be much lower.

    18. #18
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      A frequent and respected contributor to the forum has a video of a spinning pond on his Youtube channel. I will PM and ask permission to place the link here.

    19. #19
      coolwon is online now Senior Member
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      Quote Originally Posted by Jacques View Post
      To me the elusive balance lies in getting enough spin to clean the pond and distribute O2 but not too much to make the pond an uncomfortable home for the koi (with areas of the pond they avoid or dislike).
      I found O2? I added 200 mm flat air stones fixed to my bottom drain covers. 20 liters of air per 200mm of air stone.

      I got the surface water boiling like the sea surface is most times, a turbulent upside down mass of crashing white horses. Never mind the pretty placid mill pond water rotating

      slowly look. The fish can avoid currents.They struggle to find rich enough o2 water.

      The area's they avoid and dislike might be low in 02 content.

      The bottom drains benefit from the current created by the rising columns of air and draw in the dirt towards the bottom drains.

      Garfield
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      Quote Originally Posted by Jacques View Post
      A frequent and respected contributor to the forum has a video of a spinning pond on his Youtube channel. I will PM and ask permission to place the link here.
      Unbeknown to me, Norm Walsh passed on some months ago. I did not know Norm personally but got some idea of the man he was by reading his posts on this forum. He contributed much to our hobby and seeing that the video in question was posted to a public access Youtube channel, I decided to post the link: https://www.youtube.com/watch?v=fmYHnvfiGmw

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