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Thread: Let if flow!

  1. #1
    MCA
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    Let if flow!

    Oh the weather outside is frightful
    But the koi are so delightful
    And soon we are off to the show
    Let if flow! Let if flow! Let it flow!


    It doesn’t show signs of stopping
    The Gosankes are all eye popping
    The DO is not too low
    Let if flow! Let if flow! Let it flow!






    Way back when at the dawn of time, close to 15 years ago, Waddy had just released Koi Kichi and it was a brave new world as koi keepers in the West were migrating from a water gardening tradition to full on koi keeping. We were learning that the devil is indeed in the details.


    The early bottom drains with air domes were using 4” pipe, but had the air hose running up the middle of the drain pipe. The next generation, such as the Spindrifters we have, had moved the air supply to a fitting fused into the side of the sump and you had to run a tube from the from inside wall of the sump to the central column to deliver air to the diaphragm. Soon afterwards the next step in evolution was to move the air fitting to the bottom of the bottom drain sump and deliver the air to the diaphragm’s column. Those two steps separated the air delivery from the movement of water to the external filters. Definitely major steps forward.


    So now we have modern bottom drains with 4” pipe to the filters. But does 4” make sense? A 4” plastic pipe that has the length of 25, that has a 6” drop from pond level, can deliver around 11,000gph. A 3” pipe that is 25 feet long will gravity feed over 5,000gph with a 6” drop. If we design ponds to only flow around 3,000gph per drain via 4” pipe, it is not surprising that the drain lines themselves can turn into settlement areas.


    Personally, I am gonna crank it up. I am planning to use a sieve that will let me flow at least 6,000gph to the pump, bead filter, and back to the pond. At that flow rate, low cost pumps are available. If I wanted to try pump 10,000gph, then there would be a significant cost increase in the pump and in the electricity consumed.


    So what iss the net change to our pond? Today each of the two drain circuits is running around 4,000gph for a total of 8,000gph. So I am turning over the 10,000 gallon pond every 1.2 hours or 19.2 times per 24 hour day. If I increase the flows on both drains to 6,000gph, that gives a total of 12,000gph. That means I will be turning over the pond every 0.83 hours or just over 28 times per day.


    The next time you plan/build/remodel a koi pond with 4” BD pipes, consider what flow rates you want. You are definitely not limited to the range of 3-4,000gph. Naturally the desired flow rate will influence your decisions on filter types/models and on pumps. It is all about knowing your options.


    Let it flow! Let it flow! Let it flow!!!
    Koi keeping is not a belief system; it is applied science with a touch of artistry.

  2. #2
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    You're right in that we normally should only install lines that are best for the flow we intend. BD lines are a problem because we either want to minimize the drop to a sump or trying to keep pump suction low to be certain we will not approach a point of cavitation. Pumps can aid the flow and tolerate some suction head but gravity head causes the water level to drop. That drop will be accumulative if the sump moves on to another tank using that same gravity flow to draw from the sump. I recall one installation that had enough draw down to cause the last tank to drop below the exit line feeding the pump installed at the end of the line.

    the 6" drop concerns me! Any open top component receiving that water would have to be able to accommodate that drop. Lowering the component to accommodate the drop will cause most off the shelf units to over flow when the pump is turned off. That can be remedied but it's crucial that the designer know the drop before they start building the filter pit.

    As you know it's very easy to compute the drop of any line you wish. What I'm getting at is I recommend anyone building a pond prepare first by learning the basics of Pond building before hand, so they don't have to jury rig to fix a design problem or live with the impact of the problem.

    Even if you plan to hire a contractor you would be well advised to understand pond design. Many pond builders learned to get a size that works, as far as they can see, by making mistakes until the system seemed to work but they were unaware of the waste deposit created if all their ponds had 4" bottom drains as you mentioned. Another common problem is installing a larger pump to 'fix' the line too small for the purpose.

    I have installed 2 BDs and a MD with 4" lines because I want a pond I can experiment with. I purge the line several times a week because waste left in BD lines are just as unhealthy as any other waste. If I am doing a pond that's intended to be a conventional pond I would be installing the 3" lines mentioned above and have a healthier pond. But I would still be purging as much because there would still be waste dropping into the line just less waste.

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    Thank Rich. I have no idea why most open filter chambers are designed for slow flows of 4000gph or less. That does not at all match up to the 4" pipe potential. There will be settlement in the 4" line unless it is purged every week. When I put in the new sieves I will put in a T fitting after the knife valve from the 4" DB circuit. On the side of the T I will put in a 2" ball valve with the output to the filter pit drain (to the storm drain). Those 2" ball valves will let me quickly purge the BD lines and dump up to 1/3 of my pond (3' out of 8') for a large water change.

    My filters will not overflow as I use a sieve and bead filter on each BD lines.....nothing to overflow when the pump stops. My other filter is a bakki shower run fed by the skimmer. Again, nothing to overflow when the pump stops. I have a 2" overflow on the pond wall that dumps to the filter pit. That has been a good thing this year. So far we have had more rain in the first 6 months of 2013 than we had in all of 2012......and the hurricane season is far from over.

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    Interesting; I have never thought of using the filter pit as an overflow for a pond. Need to make certain the overflow doesn't damage electrical components but that's not hard.

    Good plan but won't you get a better purge with a 4" dump valve? A knife valve here would be cheaper. I don't consider knife valve reliability a problem when it's not installed with the valve handle on the top. Turning it 180 will eliminate the valve seat pit Even a 90 should eliminate the pit from the bottom where everything settles. Leaks are never a problem if it just falls to the ground as you dump many times that in your maintenance.

    I dump my beads every day and it's never a problem to purge the BD line so it happens several times a week.

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    won't you get a better purge with a 4" dump valve?

    Yes but my filter pit floor drains would not likely keep up with that flow level for very long. I can open the 3" waste valve on the new sieve and the 2" ball valve and get enough flow for long enough to clear the pipe without flooding the filter pit. I will know more when the new sieves arrive in early August.

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    It's funny! I live in an area that's considered a desert climate and we never think of a need to keep our fish from washing away.

    Same for folks in Knew York; they have to deal with winters that feeeze a pond with thick ice.

    My water's a little green!

    My earlier post was an on going attempt to encourage people to learn about the technical end of pond design. I can see a need for the KOI international training programs.

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    Agreed. I think teaching that. 4" pipe from a drain can easily deliver serious flow, well above 3-4000gph, should be one of the basics. Encourage folks to make an informed decision about filters and piping and how those decisions are part of designing foe a target flow rate.

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    The pipe flow chart I normally use can be downloaded from:
    Irrigation Association - The recognized authority on irrigation.

    The shaded areas are the flows that exceed the pipe manufacturers recommended maximum flows of 5fps.

    Look around the site, there may be info you like. I saw something about evaporation rates and a site that gives various state averages. Knowing the evaporation rate can go a long way toward predicting how much heat you need to keep a med tank warm.

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    Here is the calculator I use for flow rates based pipe size, height differential,...etc. It is handy for planning the use of sieves or other gravity flow aspects in the pond. It is amazing the potential flow rates from 4" pipe with just a 6" drop.

    CalcTool: Gravity-fed pipe flow calculator

  10. #10
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    Wow, what a great site!

    I browzed and got caught up in the variety, I can even determine the energy in a 254um photon! Oh yeah, It gives other pipe calks too!

    Great site, go visit it.

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