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  1. #1

    Pull on bottom drain

    I'm not sure my bottom drain is pulling water and waste through very well. What are the main factors that affect the pull made by the bottom drain?



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    Senior Member Rank = Mature Champion dbs's Avatar
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    Quote Originally Posted by Solo86 View Post
    I'm not sure my bottom drain is pulling water and waste through very well. What are the main factors that affect the pull made by the bottom drain?
    With mine (new pond, first pond with bottom drain) I found out that the basket in my Skimmer restricted the flow WAY too much for my Sieve to fill correctly, basket removed on Friday night and it works a treat !!

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    Senior Member Rank = Rokusai Simon Fish's Avatar
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    What height is the dome set, what's the gap?

    Less than around a half inch would start to compromise the effective area compared to pipe area, assuming a 4" pipe and a bottom drain 12-15"

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    Extreme Koi Member Rank = Adult Champion NickK-UK's Avatar
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    Quote Originally Posted by Solo86 View Post
    I'm not sure my bottom drain is pulling water and waste through very well. What are the main factors that affect the pull made by the bottom drain?
    What's the plumbing configuration?
    14000l, my mutts: Chargoi (2010), Doitsu (2022), Tancho (2022), Kujaku (2022), Hi Utusri (2022)

  6. #5
    Quote Originally Posted by Solo86 View Post
    I'm not sure my bottom drain is pulling water and waste through very well. What are the main factors that affect the pull made by the bottom drain?
    What size is your pump and where is it placed? Is there much head pressure?

    Sent from my SM-G986B using Tapatalk

  7. #6
    It's a 4" airated bottom drain. I adjusted the gap between the dome and the drain by putting my fingers between and using that as the gap. Would a bigger gap pull more?
    It comes from the bottom drain by 4" pressure pipe into my AEM mini drum. From the drum into a static bed and then pumped using a 20k pump through an ashp and then over a bakki shower. The skimmer is also gravity fed into the AEM drum by 4" pipe.

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    Moderator Rank = Supreme Champion Feline's Avatar
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    What happens when you do a drain dump (open the valve into empty drum)? Does it gush in very rapidly?

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  10. #8
    Quote Originally Posted by Feline View Post
    What happens when you do a drain dump (open the valve into empty drum)? Does it gush in very rapidly?
    Yeah it gushes in quickly.

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  12. #9
    Quote Originally Posted by Simon Fish View Post
    What height is the dome set, what's the gap?

    Less than around a half inch would start to compromise the effective area compared to pipe area, assuming a 4" pipe and a bottom drain 12-15"
    So does this mean the bigger the gap the more flow/pull?

  13. #10
    Senior Member Rank = Rokusai Simon Fish's Avatar
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    Maybe/maybe not, a finger gap or around half an inch is about equal to the cross sectional area of a 4" pipe, so the ideal equal match.
    If the gap was smaller it could then start to restrict the potential flow, hence my first question.
    Feline's question was better, if you do get a decent gush, why do you think the flow is limited?
    Maybe as others have suggested the pipe layout, pull on a skimmer might be the problem?

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  15. #11
    Senior Member Rank = Supreme Champion freddyboy's Avatar
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    My dome gap on finger size. Is set to my fingers. And I get a great flow. And gushes great. When purging. You say you get a good flow on purging. Cannot be the bottom drain. If you do. Maybe pump size.
    Is your skimmer and bottom drain to a T piece. Or do they go to drum seperate.
    Fred

    Sent from my SM-G960F using Tapatalk

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    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    What's the problem exactly,is the waterlevel low on the dirty or clean side of the drum?
    If the level is ok on the dirty side but low on the clean side the screen may need cleaning.
    If low on the dirty side is the drum at correct height?
    The drain gap will be ok if set to 1/2ins or finger thick,is the skimmer directly connected to 4ins pipe and not 1.5ins to 4ins?
    John

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  19. #13
    Hi guys. Thanks for the feedback. From all of your comments it would seem that the pull from the Bottom Drain is good. I'm getting a bit of floating material in the pond and I just wondered if that was to do with it not getting pulled through the bottom drain. Here is a diagram of my pond setup so you can see how I have set it all up. Any comments or suggestions are welcome.
    Pond Diagram v1.jpg

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  21. #14
    Hi guys. Thanks for the feedback. From all of your comments it would seem that the pull from the Bottom Drain is good. I'm getting a bit of floating material in the pond and I just wondered if that was to do with it not getting pulled through the bottom drain. Here is a diagram of my pond setup so you can see how I have set it all up. Any comments or suggestions are welcome.<br><img src="https://www.koiforum.uk/attachment.php?attachmentid=35317&stc=1" attachmentid="35317" alt="" id="vbattach_35317" class="previewthumb">

  22. #15
    Moderator Rank = Supreme Champion Feline's Avatar
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    You may have a balance problem between your skimmer and BD. Since you’ve got variable flow rate pumps it’s probably worth playing around a bit with pump speeds and valves to get the balance how you want it.

    Unfortunately the only way of knowing for sure the true flow through each individual pipe is to fit flow meters, which are very very expensive. That’s why most of us balance it by eye, and by running some tests on each feed at a time to figure out which takes the lions share of the flow if it’s valve is fully open.
    Do you have a valve on the gravity feed from your skimmer? I have a skimmer with 3” outlet and 2x 4” BDs going into my drum and I find I need to partially close the skimmer valve or it ‘steals’ a lot of flow from the drains.

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  24. #16
    Thanks Feline.
    I haven't got a valve on the skimmer line but I will fit one.

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    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    Hi Solo,
    Agree with Feline above,I would take off or close down the pump on the skimmer and valve the skimmer,with the pump on there it is actually pulling more on the skimmer try turning it off.

    Just looked at the Aem and it only has one outlet which is a pain but can cope with a 4400 gal flow.
    Seems to me there is a big flow on the bio ( what size is the bio ) you could put a T on the drum outlet to go to shower or asap, and the bio only useing 2 pumps.

    This wont effect your drain pull but the skimmer suggestion will.
    Try switching the skimmer pump off and put a short piece of 3ins pipe down the skimmer outlet to restrict it and see what that does,that will make the bottom drain pull.

    Great diagram sketch.
    John

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  30. #19
    Senior Member Rank = Rokusai Steve's koi's Avatar
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    Personally I would take the Tee out between the Bakki and the skimmer pump, and put an elbow in It's place so the ASHP and static bed feed the bakki only, and do away with the skimmer pump, as that is possibly pulling water from the RDF as well as the skimmer.

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