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  1. #1

    Gravity retro drain using 40mm pipe?

    HI All.

    I am moving house soon and i've bought a 9000 litre steel frame pool to house my fish for about a year. I currently have a 4 bay cloverleaf filter which is pump fed pulling through a retro bottom drain.

    The new pool is 1.2m high and I don't fancy lifting my huge filter up that high so i'd like to convert it to gravity fed. I was hoping to copy this retro bottom drain feeding through a bulkhead.
    sg discharge via single 90 - 1.jpg

    Question: Is 40mm pipe large enough to feed the filter via gravity? My pump is 12000lph.



  2. #2
    Extreme Koi Member Rank = Gosai Andymadd's Avatar
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    Mar 2011
    Thanks / Likes
    Simple answer is no, 4inch or 110mm min

  3. #3
    Quote Originally Posted by Andymadd View Post
    Simple answer is no, 4inch or 110mm min
    Dammit. I figured it would as I currently use 40mm pipe as a gravity return and that looks like it could handle 2x what is currently moving down it (approx 11k lph). Ok back to the drawing board. Thanks

  4. #4
    Extreme Koi Member Rank = Mature Champion Andre Asagi's Avatar
    Join Date
    Apr 2014
    Tosche Station....Picking Up Some Power Convertors
    Thanks / Likes
    Agree. Not a chance with 40mm. I think the image you posted uses 110mm but it does look smaller.

  5. #5
    Senior Member Rank = Supreme Champion Ajm's Avatar
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    Mar 2018
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    Dracodrum retro bd runs 90mm to use as gravity

    Sent from my F5121 using Tapatalk



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