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  1. #1

    Max Flow Rate Through 2" Bottom Drain and Piping

    Evening all

    Come spring I am looking to increase my flow rate through my filtration, two reasons:

    1. to increase the waste pull to the bottom drain in the pond
    2. increase the turn over from 1x to 2x

    My pond is 1500 gallons, I have a 2" bottom drain and 2" piping through out. Gravity fed static k1 into fluid bed filter chamber.

    Is there a way to calculate what my max flow rate can be, avoiding running the fluid bed dry?

    Thank you

    Kelvin



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  3. #2
    Senior Member Rank = Grand Champion andikoi's Avatar
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    what size pump do you have now?? you could buy a variable speed pump that at its lowest is what you have now and just turn it up,leave an hour and if ok turn up again,until it runs the bed dry,i used to pull 15000lph through 3" pipe to a sieve and it worked ok,andi

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  5. #3
    There is a couple of people on the forum that can do these types of calculations, but that person ain't me!

    20,000 lph pumps come with 2" fittings so I'd guess that would indicate the potential flow.

    But I also suspect the maximum flow is specific to a particular set up in view of pipe bends and distance of pipe and water pressure over the bottom drain (i.e a 20 foot deep pond will send more water through a 2" bottom drain than a 2 foot deep pond).

    The easy option is to try what Andi suggests above.

    An alternative would be next time you do a partial water change, mark the pond at that reduced level then count how many litres it uses to top up, then on the next partial change empty the pond via the bottom drain and time how long it takes the water to go down to the line you drew. From that you can calculate how many litres per hour your specific bottom drain is capable of removing via gravity alone.

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  7. #4
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Quote Originally Posted by KC225 View Post
    Evening all

    Come spring I am looking to increase my flow rate through my filtration, two reasons:

    1. to increase the waste pull to the bottom drain in the pond
    2. increase the turn over from 1x to 2x

    My pond is 1500 gallons, I have a 2" bottom drain and 2" piping through out. Gravity fed static k1 into fluid bed filter chamber.

    Is there a way to calculate what my max flow rate can be, avoiding running the fluid bed dry?

    Thank you

    Kelvin
    hi kelvin,

    the maths this on this is that you will only be able to gravity feed a quarter of the flow through 2”that can be drawn through 4”... Go beyond 30k l/hr with 4” and the head loss becomes significant, so I would suggest the max actual flow you can draw through 2”is circa 7500l/ hr.

    Dave

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  9. #5
    Extreme Koi Member Rank = Adult Champion pip895's Avatar
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    the factor of 4 is actually over generous as it doesn't take account of additional losses due to increased friction in the smaller pipe.

    My experience is that getting more than 15k actual flow through a 4" drain creates quite a big drop. Admittedly I don't have the shortest runs but at least I only have 1 90 deg bend..


    Using Dave's calculation on that would only give you 3450ltrs/hr so a turnover of approximately once per 2 hrs! That is why gravity feeding should be with 4" or 3" pipes at the very least!
    6000g unheated in ground koi pond
    +3000g lily/Anoxic pond attached
    28 koi (40 to 65cm)
    Bottom drain & Skimmer to Drum
    JBR boichamber->Blue eco 500 pump ->below surface return.
    Blue Eco 240 -> Large MB -> Waterfall -> Planted Anoxic pond (25 baskets)

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  11. #6
    Extreme Koi Member Rank = Gosai davec's Avatar
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    I had a gravity fed skimmer on 2 inch into my drum and the flow was rubbish i had it converted to 3 inch a few weeks ago and the difference is unbelievable

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  13. #7
    CHeers all

    I definitely agree that bigger would have been better, however as it is I will need to stay on a constant diet to get into the crawl space where the piping resides. I have tried to build the biggest volume pond with the space available without cutting corners or compromising on quality. But at the same time it needed o be practical as I am not staying here forever. Link to build https://www.youtube.com/watch?v=Io-h5EBmdvo&t=29s

    I have a 5000 on it at the moment and only have one 90 degree bend, which is under that wooden step in the 1st pic.

    My only route might be to get a variable and see what flow rate I can achieve or borrow a larger pump to test.

    20181212_151524.jpg20181212_152801.jpg20181212_152743.jpg

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  15. #8
    It sounds like I'm unlikely to get that 2x that I would like. In regards to the best possible biological filtration, there have been various discussions on whether turn over is still the way forward or whether the longer settlement period is more effective. What's the thoughts on this now?

    Secondly, what would people recommend as a good variable pump which can be tuned down to at least 6000ltrs and I suppose the max would be 10,000 if I'm lucky?

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  17. #9
    Extreme Koi Member Rank = Gosai davec's Avatar
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    Jebao 10000 vari flow are pretty good value for money £109 on amazon I think

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  19. #10
    Quote Originally Posted by KC225 View Post
    It sounds like I'm unlikely to get that 2x that I would like. In regards to the best possible biological filtration, there have been various discussions on whether turn over is still the way forward or whether the longer settlement period is more effective. What's the thoughts on this now?

    Secondly, what would people recommend as a good variable pump which can be tuned down to at least 6000ltrs and I suppose the max would be 10,000 if I'm lucky?
    I think that you have to be careful here, by thinking that the only water turnover rate that works is 1 hour !
    The is no right or wrong on turnover due to pond size, filtration etc etc. We all know that the suggested turnover for a shower is thought to be around an hour, but showers still work very well with a two hour turnover, it again is variable due to feeding quantities, fish size and quantity of fish..

    With your K1 fluid bed, I would say that a two hour turnover is about as it should be in my opinion, having run a 400ltr K1 filter for the last 7 years, with big fish and heavy feeding, and without a parameter glitch ever during this time, my two hour turnover suits my set up perfectly.

    You also have to remember the other aspect, which is the fish. Koi are not fast water fish, so to turn water over in one hour through a 2 " pipe, the agitation will be very fierce, for a fish that is most comfortable in slow moving water.......always remember its should always be about the fish being happy !!

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  21. #11
    Senior Member Rank = Grand Champion andikoi's Avatar
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    have you a photo of your filter setup,looking at your first pic im guessing the sloping pipe from floor is from bd to filter,how long is that pipe,on my old pond when i fitted my first bd i used a 4" bd but got told to use 3" pipe to avoid crud build up,worked well but when i moved all my filters to new filter house after raising pond walls and digging deeper,i ended up with a 12m pipe run lol,the 3" just wasnt good enough so enlarged to 4" pipe from ground level 9m to filters,it worked well until my new pond build this year,is that a possibility,could you go bigger pipe from ground level to filters to aid with flow in,also are your static and fluid bed chambers seperate entities or is it one filter with 2 chambers,??i recomment the jeboa's aswel i run 2 and had no issues and mine are about 5 years old,andi

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  23. #12
    Quote Originally Posted by Fishplanetkoi View Post
    I think that you have to be careful here, by thinking that the only water turnover rate that works is 1 hour !
    It was more food for thought/discussion but I would always ideally aim for 2x.

    Andi, no I don't I will get a pic at the weekend. It's a homemade two chamber filter, static K1 (est. 40ltr) and fluid K1 (est. 100+ltrs). I have run this for about 10 years including the K1 (nice and mature) but prior to my move it was pump fed, so I rebuilt it to work with the gravity feed and improved the waste exits. Simple but extremely effective!

    Yes, the diagonal pipe is from the BD to the filter and only about 1.5m/2m, and under that step I also have a valve to flush the BD.

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  25. #13
    Extreme Koi Member Rank = Supreme Champion Davej's Avatar
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    Quote Originally Posted by KC225 View Post
    It sounds like I'm unlikely to get that 2x that I would like. In regards to the best possible biological filtration, there have been various discussions on whether turn over is still the way forward or whether the longer settlement period is more effective. What's the thoughts on this now?

    Secondly, what would people recommend as a good variable pump which can be tuned down to at least 6000ltrs and I suppose the max would be 10,000 if I'm lucky?
    Hi Kelvin

    There will always be an optimum for the particular set up an load on it. Personally I favour lengthy retention periods in the chambers but also a turnover through the filters every 20-30 minutes; the end result being large chambers! It is not for everyone I know but its the best I have yet found for the stock and feed I use.

    In a smaller volume of water things are always going to be more challenging and personally I favour slightly faster turnover, if not you can see fairly hefty swings in the "background" pollutant levels during the feeding day - with the filters then playing catch up over night.

    Dave

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