Announcement

Collapse
No announcement yet.

Bottom Drain Functionality ??? Help me understand...

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Bottom Drain Functionality ??? Help me understand...

    My understanding is………

    … in designing a bottom drain, the size drain pipe used (3” or 4” as it may be) and the depth at which the pipe is placed in the settlement tank relative to the pond’s water level, will determine the “flow” rate at which the drain will collect the pond water into the settlement tank. This is also dependent upon the pump size returning water to the pond which is situated at the ‘end of the line’ so to speak. (Am I on the right track here?)

    If I am following the logic thus far, then if a 4” drain pipe is used at a certain depth relative to the pond’s water level, the flow rate might be equal to say 3500 gph, thus requiring the settlement tank to be something like 350 gal at a minimum [what I’m getting at here is the settlement tank has a minimum gallon required based on what the drain is feeding it???). (Am I making any sense?)


    Ok, if I’m somehow on the right track, then my question is: if I were to use “two” 4” bottom drains, going into the same (?) settlement tank, would this settlement tank now need to be a minimum of 700 gals at a minimum to allow for both bottom drains to draw the 3500x2=7000 gph?


    I want to make sure I understand the 'physics' of a bottom drain --- why it works and how it works --- so that in designing pond #2 I will be able have a good understanding of how it is suppose to be planned for and setup.....


    Rita





    "...no matter how you look at it, Mother Nature still makes the rules."
  • #2

    Originally posted by KoiKisses View Post
    My understanding is………

    … in designing a bottom drain, the size drain pipe used (3” or 4” as it may be) and the depth at which the pipe is placed in the settlement tank relative to the pond’s water level, will determine the “flow” rate at which the drain will collect the pond water into the settlement tank. This is also dependent upon the pump size returning water to the pond which is situated at the ‘end of the line’ so to speak. (Am I on the right track here?)

    If I am following the logic thus far, then if a 4” drain pipe is used at a certain depth relative to the pond’s water level, the flow rate might be equal to say 3500 gph, thus requiring the settlement tank to be something like 350 gal at a minimum [what I’m getting at here is the settlement tank has a minimum gallon required based on what the drain is feeding it???). (Am I making any sense?)


    Ok, if I’m somehow on the right track, then my question is: if I were to use “two” 4” bottom drains, going into the same (?) settlement tank, would this settlement tank now need to be a minimum of 700 gals at a minimum to allow for both bottom drains to draw the 3500x2=7000 gph?


    I want to make sure I understand the 'physics' of a bottom drain --- why it works and how it works --- so that in designing pond #2 I will be able have a good understanding of how it is suppose to be planned for and setup.....


    Rita




    Hi Rita,
    I "think" you have about half of it. Let me try and explain.

    Any two bodies of water (like a settlement tank and pond) connected by a pipe will seek the same elevation or level of water. You with me so far?

    OK, now if I draw water from one body of water (the settlement tank), and return it to the other, the settlement tank water elevation will lower based on two factors as the water levels "attempt" to even out. The "draw down (or differences in water level) from the settlement tank to the pond is dependent on pipe size and the amount of water (rate of which) the water is being removed from the settlement tank. The larger the pipe size, the less difference in water levels. Gravity is what is forcing water from the pond to the settlement tank based on the ddifference in water levels.

    Now, if I haven't lost you yet, the height of the bottom drain itself is not an issue since the only force(gravity) acting upon the body of water is that created from the difference in water elevations between the two tanks (pond and settlement chamber).

    OK, you still with me here?

    You can trust me here or you can go through all of the math yourself but a 4" pipe and a 1" difference in water levels will be about 3850 US GPH (minus piping friction losses). I typically use 3500 GPH as the base number for a 4" pipe with a 1" drawdown.

    In ther words, if a pump is pumping arund 3500 GPH from one tank that is conected to another tank by a 4" line, then there will be about a 1" difference in water levels while the pump is running. Turn the pump off and the water levels will equalize.

    Now for the next step if I haven't lost you yet. That 1" drop will happen for EACH subsequent transfer as well. so for a popnd to 3 chamber filter system, the pond will be 3" higher than the last chamber/transfer when the pump is pumping 3500 GPH. If the suction point for the pump n the last chamber is say, 2" below non running water level, guess what happens.....the pump can't get enough water!

    Does all of this make sense?

    One of the reasons you'll hear many hobbyists prefer 4" drains over 3" drains is that a 4" drain can carry substantially more water with less draw down than a 3" drain. I'll try and post the amount tonight along with some diagrams that may also help your understanding.

    Steve
    The views presented are my personal views and not that of any organization that I may belong to unless otherwise specified. sch[email protected]
    CKHPA

    Comment

    • #3

      Whoops too slow I see Steve was all over it while I was typing


      Simply stated, the water in the SC seeks equilibrium with the pond level no matter what your pond depth is. The 10% rule for SC to pond size is a rule of thumb for dwell time in SC for solids to settle out. From a flow stand point the Pump flow determines the rate of flow through bottom drain piping up to the limitation of that Pipe's gravity flow rate which in this application you needn't worry about. Max gravity flow for 3" 7200gph, 4"-12,000gph excluding dynamic head losses.

      Comment

      • #4

        Originally posted by schildkoi View Post
        Hi Rita,
        I "think" you have about half of it. Let me try and explain.

        Any two bodies of water (like a settlement tank and pond) connected by a pipe will seek the same elevation or level of water. You with me so far?

        OK, now if I draw water from one body of water (the settlement tank), and return it to the other, the settlement tank water elevation will lower based on two factors as the water levels "attempt" to even out. The "draw down (or differences in water level) from the settlement tank to the pond is dependent on pipe size and the amount of water (rate of which) the water is being removed from the settlement tank. The larger the pipe size, the less difference in water levels. Gravity is what is forcing water from the pond to the settlement tank based on the ddifference in water levels.

        Now, if I haven't lost you yet, the height of the bottom drain itself is not an issue since the only force(gravity) acting upon the body of water is that created from the difference in water elevations between the two tanks (pond and settlement chamber).

        OK, you still with me here?

        You can trust me here or you can go through all of the math yourself but a 4" pipe and a 1" difference in water levels will be about 3850 US GPH (minus piping friction losses). I typically use 3500 GPH as the base number for a 4" pipe with a 1" drawdown.

        In ther words, if a pump is pumping arund 3500 GPH from one tank that is conected to another tank by a 4" line, then there will be about a 1" difference in water levels while the pump is running. Turn the pump off and the water levels will equalize.

        Now for the next step if I haven't lost you yet. That 1" drop will happen for EACH subsequent transfer as well. so for a popnd to 3 chamber filter system, the pond will be 3" higher than the last chamber/transfer when the pump is pumping 3500 GPH. If the suction point for the pump n the last chamber is say, 2" below non running water level, guess what happens.....the pump can't get enough water!

        Does all of this make sense?

        One of the reasons you'll hear many hobbyists prefer 4" drains over 3" drains is that a 4" drain can carry substantially more water with less draw down than a 3" drain. I'll try and post the amount tonight along with some diagrams that may also help your understanding.

        Steve
        Originally posted by MikeS View Post
        Whoops too slow I see Steve was all over it while I was typing


        Simply stated, the water in the SC seeks equilibrium with the pond level no matter what your pond depth is. The 10% rule for SC to pond size is a rule of thumb for dwell time in SC for solids to settle out. From a flow stand point the Pump flow determines the rate of flow through bottom drain piping up to the limitation of that Pipe's gravity flow rate which in this application you needn't worry about. Max gravity flow for 3" 7200gph, 4"-12,000gph excluding dynamic head losses.

        Thank you guys for the quick response. I'm going to read through the information you provided, and see if I can get my head around it. I'm sure I'll have more questions, but I need to absorb what you've given me thus far .....

        Thanks again,

        Rita
        KoiKisses
        "...no matter how you look at it, Mother Nature still makes the rules."

        Comment

        • #5

          Going with 4" is definitely worth the effort as you can see from the info Mike gave that the 4" line will carry nearly double the volume of a 3" line.
          Larry Iles
          Oklahoma

          Comment

          • #6

            Wow, no wonder I have had so much trouble with the 2" tetra BD I have. Anyone have the flow numbers for 2" off the top of your head?

            Comment

            • #7

              Originally posted by JTParts View Post
              Wow, no wonder I have had so much trouble with the 2" tetra BD I have. Anyone have the flow numbers for 2" off the top of your head?
              Roughly 1/2 as much as a single 3".
              Sucks don't it
              Larry Iles
              Oklahoma

              Comment

              • #8

                Originally posted by PapaBear View Post
                Roughly 1/2 as much as a single 3".
                Sucks don't it

                Um...YEAH! I have to supplement flow back to the SC, which is diminishing the SC effectiveness due to irregular currents. Need to pull everything apart and go with 3" min.

                Anyone have any experience modding a 2" retro BD to a 3"? I guess I should just sell the 2" and step up.

                Comment

                • #9

                  Originally posted by JTParts View Post
                  Um...YEAH! I have to supplement flow back to the SC, which is diminishing the SC effectiveness due to irregular currents. Need to pull everything apart and go with 3" min.

                  Anyone have any experience modding a 2" retro BD to a 3"? I guess I should just sell the 2" and step up.
                  If you are going to change away from the 2", then go with the 4". Skip the 3".

                  Steve
                  The views presented are my personal views and not that of any organization that I may belong to unless otherwise specified. [email protected]
                  CKHPA

                  Comment

                  • #10

                    I'll also add dwell times since you were referencing the settlement tank size.

                    Dwell time is basically the amount of time the water spends in the settlement chamber before moving to the next chamber/pump. Simply described, if you took something nuetrally bouyant and allowed it into the pipe and then timed how long it took for the item to exit the chamber it would give you your dwell time.... OR... If you're flowing 3500 GPH or 58.3 GPM and your settlement chamber is 58.3 gallons big, you've basically got 1 min. of dwell time.

                    Obviously, the slower the water moves through settlement (ie. longer dwell time) the more solids will settle out of suspension and remain in the settlement chamber which will deliver cleaner water to your bio filters allowing them to work better. As a starting point you can shoot for 3-4 min.... and again, the longer the better. Now if you incorporate a vortex settlement chamber instead of raceway you're going to get better settlement in a given dwell time... I don't have a vortex so maybe others can give you a dwell time to shoot for since I haven't had a chance to play with it at all...

                    Grant

                    Comment

                    • #11

                      Originally posted by KoiKisses View Post
                      I'm sure I'll have more questions, but I need to absorb what you've given me thus far .....
                      Don't worry about asking Steve questions, he's used to me.

                      4" is definitely the way to go as long as you have a pump large enough to handle the flow. If the pump is too slow, the pipe becomes a SC of sorts and collects trash.
                      The views expressed above are my own personal views and, as such, do not necessarily reflect the views of the AKCA or the KHA program.
                      SANDY

                      Comment

                      • #12

                        [QUOTE=kntry;140464]Don't worry about asking Steve questions, he's used to me.

                        4" is definitely the way to go as long as you have a pump large enough to handle the flow. If the pump is too slow, the pipe becomes a SC of sorts and collects trash.[/QUOTE]

                        Not exactly true Sandy. Settlement occurs when the velocity of water is reduced, typically not when it is increased.

                        If the velocity of the water entering the drain is less than the velocity of the water moving through the piping, settlement is minimized. That is why the gap pf the drain dome is set so that the area/gap around the circumference is more than the crosssectional area of the piping. Additionally, regardless of the pipe size, it is good to have a T assembly or other means to flush the piping.

                        Steve
                        The views presented are my personal views and not that of any organization that I may belong to unless otherwise specified. [email protected]
                        CKHPA

                        Comment

                        • #13

                          Originally posted by PapaBear View Post
                          Going with 4" is definitely worth the effort as you can see from the info Mike gave that the 4" line will carry nearly double the volume of a 3" line.
                          Thanks PapaBear, as always. ... I feel like I got a pat on the back .... as I had already learned from my readings that the 4" was the way to go. (Yey! I got something right!)


                          Originally posted by gcuss View Post
                          I'll also add dwell times since you were referencing the settlement tank size.

                          Dwell time is basically the amount of time the water spends in the settlement chamber before moving to the next chamber/pump. Simply described, if you took something nuetrally bouyant and allowed it into the pipe and then timed how long it took for the item to exit the chamber it would give you your dwell time.... OR... If you're flowing 3500 GPH or 58.3 GPM and your settlement chamber is 58.3 gallons big, you've basically got 1 min. of dwell time.

                          Obviously, the slower the water moves through settlement (ie. longer dwell time) the more solids will settle out of suspension and remain in the settlement chamber which will deliver cleaner water to your bio filters allowing them to work better. As a starting point you can shoot for 3-4 min.... and again, the longer the better. Now if you incorporate a vortex settlement chamber instead of raceway you're going to get better settlement in a given dwell time... I don't have a vortex so maybe others can give you a dwell time to shoot for since I haven't had a chance to play with it at all...

                          Grant

                          THANKS GRANT! I knew there was a dwell time factor, but hadn't got my thoughts around that yet. NOW I CAN!
                          "...no matter how you look at it, Mother Nature still makes the rules."

                          Comment

                          • #14

                            [QUOTE=schildkoi;140465]
                            Originally posted by kntry View Post
                            Don't worry about asking Steve questions, he's used to me.

                            4" is definitely the way to go as long as you have a pump large enough to handle the flow. If the pump is too slow, the pipe becomes a SC of sorts and collects trash.[/QUOTE]

                            Not exactly true Sandy. Settlement occurs when the velocity of water is reduced, typically not when it is increased.

                            If the velocity of the water entering the drain is less than the velocity of the water moving through the piping, settlement is minimized. That is why the gap pf the drain dome is set so that the area/gap around the circumference is more than the crosssectional area of the piping. Additionally, regardless of the pipe size, it is good to have a T assembly or other means to flush the piping.

                            Steve


                            Thanks Steve! ....I'm gonna add this to my other informatin too and see if I can put it all together!
                            "...no matter how you look at it, Mother Nature still makes the rules."

                            Comment

                            • #15

                              Originally posted by JTParts View Post
                              Um...YEAH! I have to supplement flow back to the SC, which is diminishing the SC effectiveness due to irregular currents. Need to pull everything apart and go with 3" min.

                              Anyone have any experience modding a 2" retro BD to a 3"? I guess I should just sell the 2" and step up.
                              Have only used the Aqua Art retro myself but you would have no problem with a 2-3 or 2-4" increaser at the drain itself. On a side not make sure your retro is well weighted down, don't want to see any fish rolling around in your priming pot. Don't ask me how I know this That being said, a proper bottom drain would be a big improvement for you, I only use the retro in QT.

                              Comment

                              All content and images copyright of: Koi-bito.com
                              Working...
                              X