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Thread: Let if flow!

  1. #11
    Jumbo Appliance Guy's Avatar
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    Pond is two years old. I use two 4" BD's that tee into a Cetus Sieve. Originally I used an ES 8500, but even with lowering the unit I was getting pump cavitation. So I switched to an ES5500. I purge the Cetus at least weekly and flush the drain lines every few months by valving off one line and flushing than doing the same for the other line. Now interestingly, I recently had a buddy jump in the pond with the purpose of removing the aerator domes and inspecting the drains for rocks, stones and other debris... What was a surprise was that there was little debris- less than a cup worth. I did get some koi teeth and two pieces of liner that was waded up, but mostly it was grit from the 400#'s of feather rock in my showers. I thought it to be unusual that there was very little debris. When the pond was first set-up I got feather rock size chunks the size of cherry tomato... There is a lateral 4' run and 8' run from the drains to the elbow going up...I suppose there could be debris in that area that I am unable to get out???? The BD's are located approx 5' below the output of the sieve (as it overflow the weir). So a pretty good draw at 5'...

    BUT- I think I can do better, so I am adding a second Cetus and pump and am reconfiguring my plumbing so that the sieves are direct return to the TPR (one from each sieve pump). I'll then gravity drain each sand gravel filter onto the shower, rather then the shower being fed from the sieves... I am thinking this should get the bottom drains moving even better. Let it flow, let it flow, let it flow....

  2. #12
    Tosai
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    Excellent points, I have an even more abnormal situation with my pond. My system is a pump-up design, so my pumps draws suction from my drain and skimmer. My pump is effectively going to move however much water it wants, assuming I'm not using itsy bitsy pipe, so a 4" drain is simply silly for me. My 1.5" drain line is able to easily handle 4000gph, multiplied by two for my skimmer suction (the two lines merge into 2"). As I do not pump anything near 8000gph, running anything larger than that is just more money and more places to grow nasties.

  3. #13
    Tategoi
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    I'm missing something here! Those lines are not rated for that much flow, especially supplying to pump suction of what I'm assuming is a 1/4hp pump suction enc pump. What pump are you supplying and how long is each of the lines?

    Rich

  4. #14
    Jumbo Appliance Guy's Avatar
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    Quote Originally Posted by KoiJuno View Post
    My pump is effectively going to move however much water it wants, assuming I'm not using itsy bitsy pipe, so a 4" drain is simply silly for me. My 1.5" drain line is able to easily handle 4000gph, multiplied by two for my skimmer suction (the two lines merge into 2"). As I do not pump anything near 8000gph, running anything larger than that is just more money and more places to grow nasties.
    Incorrect. You want twice the size of the pump inlet. So If you have a 1.5" pump housing you would want to use 3" pipe. You want the pump to have as little to 'pull' from the source as possible. We simplify this by suggesting twice the pump inlet size.

  5. #15
    Honmei ricshaw's Avatar
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    I have never heard that the pipe on the pump inlet side needs to be twice the size of the pump inlet size.
    I have heard that you would want to use 3" pipe (or larger) for pond bottom drain plumbing.
    I agree that you want the pump to have as little restriction from the source as possible.
    1.5" is too small for a bottom drain pipe.

  6. #16
    Tosai
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    Quote Originally Posted by Appliance Guy View Post
    Incorrect. You want twice the size of the pump inlet. So If you have a 1.5" pump housing you would want to use 3" pipe. You want the pump to have as little to 'pull' from the source as possible. We simplify this by suggesting twice the pump inlet size.

    I can show you the math if you want It's all about flow velocity. Clearly a pump can only work with so much negative head, and having smaller suction lines certainly increases your suction head, but matching pump suction dia. and inlet pipe dia is no problem unless you have very long runs to the pump. My systems runs two 1.5" suctions merging into a 2" line which feeds my pumps 1.5" inlet. A 2" line moving 3,000gph will have a flow velocity of a whopping 1.55m/s, or 3.5mph. Not exactly huge numbers there. With such a low flow velocity, the friction coefficient of the pipe is negligible, negating any hard 90's in the system.

  7. #17
    Tosai
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    Quote Originally Posted by ricshaw View Post
    I have never heard that the pipe on the pump inlet side needs to be twice the size of the pump inlet size.
    I have heard that you would want to use 3" pipe (or larger) for pond bottom drain plumbing.
    I agree that you want the pump to have as little restriction from the source as possible.
    1.5" is too small for a bottom drain pipe.

    That is certainly true if you're gravity feeding the drain. If you are pumping directly from the drain, smaller pipe is fine. There is no benefit between 1.5", 2", or 3" at the lower flow rates we're talking about. Obviously you won't be pulling 5k+ through a 1.5" line.

  8. #18
    Jumbo Appliance Guy's Avatar
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    Quote Originally Posted by KoiJuno View Post
    I can show you the math if you want It's all about flow velocity. Clearly a pump can only work with so much negative head, and having smaller suction lines certainly increases your suction head, but matching pump suction dia. and inlet pipe dia is no problem unless you have very long runs to the pump. My systems runs two 1.5" suctions merging into a 2" line which feeds my pumps 1.5" inlet. A 2" line moving 3,000gph will have a flow velocity of a whopping 1.55m/s, or 3.5mph. Not exactly huge numbers there. With such a low flow velocity, the friction coefficient of the pipe is negligible, negating any hard 90's in the system.

    Nah- I'm good. Good luck!

  9. #19
    Jumbo Appliance Guy's Avatar
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    Quote Originally Posted by ricshaw View Post
    I have never heard that the pipe on the pump inlet side needs to be twice the size of the pump inlet size.
    I have heard that you would want to use 3" pipe (or larger) for pond bottom drain plumbing.
    I agree that you want the pump to have as little restriction from the source as possible.
    1.5" is too small for a bottom drain pipe.
    Three out of four's not bad. And I suppose I should clarify that as the pipe diameter increases, the volume does not increase by the same factor. A 1/2 is pipe is not half as much as a 1" pipe. A 1" pipe is not half as much as a 2" pipe, etc... What I do suggest is 3" line from the skimmer to pump. Also size your bottom drain plumbing to correct size for the application. If the BD is pump fed, a 3" line is what I suggest, not a 2" and not a 4"- a 3" line from BD to pump if pump fed.

    I made the mistake of using 2" line from my skimmer to the pump. Like KoiJuno, I too thought a 2" skimmer line to my 1.5" pump intake would be more than enough. I was educated on the matter and now regret that decision. In fact, I am re-plumbing the skimmer to 3" when I rework my pond later this year. I just want to educate others so that they don't make the error I made. Another error I made was thinking two 4" BD's using an 8500gph pump would be sufficient. Wrong again!

    This should be Michael's mantra! "Let it flow, let it flow, let it flow...."

  10. #20
    Tosai
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    Quote Originally Posted by Appliance Guy View Post
    Three out of four's not bad. And I suppose I should clarify that as the pipe diameter increases, the volume does not increase by the same factor. A 1/2 is pipe is not half as much as a 1" pipe. A 1" pipe is not half as much as a 2" pipe, etc... What I do suggest is 3" line from the skimmer to pump. Also size your bottom drain plumbing to correct size for the application. If the BD is pump fed, a 3" line is what I suggest, not a 2" and not a 4"- a 3" line from BD to pump if pump fed.

    I made the mistake of using 2" line from my skimmer to the pump. Like KoiJuno, I too thought a 2" skimmer line to my 1.5" pump intake would be more than enough. I was educated on the matter and now regret that decision. In fact, I am re-plumbing the skimmer to 3" when I rework my pond later this year. I just want to educate others so that they don't make the error I made. Another error I made was thinking two 4" BD's using an 8500gph pump would be sufficient. Wrong again!

    This should be Michael's mantra! "Let it flow, let it flow, let it flow...."
    What problems did you have with a 2" line? What were your flow rates? As someone with extensive training and operational experience in fluid system theory, I can say with a high degree of certainty that you should not have had any problems. Assuming it was not a very long run of pipe and your flow rates were in line with the size of the pipe and the head loss of your system. My 2" suction line works swimmingly

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