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  1. #1

    Filter chamber starvation?

    Hi all,

    Filled up pond today for the first time and gravity fed combi drum. Filled the whole system so that the level in the pond was the same as the drum level. Switched on return pump at a slow rpm (variable unit) and all was fine. When I increased the return pump flow, the water in the combi drum unit dropped considerably and stayed there. Does this mean the water coming from the pond into the filter is not sufficient enough for my return flow rate?



  2. #2
    Member Rank = Nisai ganroob's Avatar
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    Firstly, congrats on filling the pond.

    As first one here I can only offer general pointers to the problem, other members will follow with more specific answers but they will need details of pump, drum and pond size.

    1/ Are the pipes big enough to allow suffient flow ?
    2/ Are they partially blocked ?
    3/ Is the drum mesh blocked with film appied during the manufacture ? Can you pressure wash it to clean it and allow proper flow of water ?

    Good luck, it will get sorted with help from all the brains on this forum.

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  4. #3
    Hi Granroob,

    Probably best to look on my construction thread..... 10, 000 gallon pond on a slope. There is, all the info there if that's OK and makes it easier for the info. Thanks

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  6. #4
    Senior Member Rank = Supreme Champion freddyboy's Avatar
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    Quote Originally Posted by Mabbs View Post
    Hi Granroob,

    Probably best to look on my construction thread..... 10, 000 gallon pond on a slope. There is, all the info there if that's OK and makes it easier for the info. Thanks
    When I 1st got my first draco drop in drum. I had same problem.
    Took me two days to fathom it out.
    Turns out that it had a mesh protection coat on the mesh. Pressure washed the mesh. And that sorted it out.
    Could be that.
    Fred

    Sent from my SM-G960F using Tapatalk

  7. #5
    Quote Originally Posted by freddyboy View Post
    When I 1st got my first draco drop in drum. I had same problem.
    Took me two days to fathom it out.
    Turns out that it had a mesh protection coat on the mesh. Pressure washed the mesh. And that sorted it out.
    Could be that.
    Fred

    Sent from my SM-G960F using Tapatalk
    I can't see any restrictions. The unit is second hand so we have it a good clean out when we got it. There was quite a bit of crap on the baffle but we got all that off

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  9. #6
    OK, so i have two returns to the combi drum filter. I just shut the valve off from the bottom drain and the water level in the combi drum stayed the same. I then opened the bottom drain valve and closed the skimmer line and the water dropped,. The flow coming through bottom drain line is no where near as fast as the skimmer!! I assume I have a blockage or and air lock in the bd line. I have tried opening and shutting the valves and small bit of air came out but nothing major. Any suggestions?

  10. #7
    Senior Member Rank = Hassai Mike Bass's Avatar
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    Quote Originally Posted by Mabbs View Post
    OK, so i have two returns to the combi drum filter. I just shut the valve off from the bottom drain and the water level in the combi drum stayed the same. I then opened the bottom drain valve and closed the skimmer line and the water dropped,. The flow coming through bottom drain line is no where near as fast as the skimmer!! I assume I have a blockage or and air lock in the bd line. I have tried opening and shutting the valves and small bit of air came out but nothing major. Any suggestions?
    if you believe there maybe an airlock try forcing extra water down the BD using water under pressure via a hose pipe ( worked for me when airlock in skimmer pipe)

  11. #8
    Senior Member Rank = Kyusai Sim's Avatar
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    Have you also left a big enough gap between the lid and pond floor on the bottom drain, mines about 2cm.

  12. #9
    Just tried the hose trick and pushed it down as far as possible. It did remove some air and the flow is a bit better, enough now so that I can shut the skimmer line off and just have return through the bd. It's still not good enough and not as flowing as the skimmer. I am sending my son in to remove the cap and push a hose down that way. I did leave a good 20cm gap on the cover but will check..... Will keep you posted

  13. #10
    Senior Member Rank = Hassai Mike Bass's Avatar
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    Quote Originally Posted by Mabbs View Post
    Just tried the hose trick and pushed it down as far as possible. It did remove some air and the flow is a bit better, enough now so that I can shut the skimmer line off and just have return through the bd. It's still not good enough and not as flowing as the skimmer. I am sending my son in to remove the cap and push a hose down that way. I did leave a good 20cm gap on the cover but will check..... Will keep you posted
    It may be the flow is slow enough to allow sediment to block some of the BD pipe. You might be able to back flow the pipe with the hose from the drum intake chamber ( if you can stop back flow from bio chamber with plastic plate or old koi food tub/yogurt pot for example) If it is due to sediment build up you may have to have add additional bypass of the bio chamber to increase the flow through the drum.

  14. #11
    OK, done lots of bits on the pond today and spent some time trying to resolve the blockage/airlock. We have pushed a hose pipe down from the filter, probably a good 2 meters down the line and turned on hose. Can't really say it has improved the flow. Jumped in pond and removed bd cap. Pushed the hose pipe up about 2 meters and turned on tap. Again, hasn't really done anything. So at this point I put the pump on full throttle and kept opening and closing the gate valve. This has some success and some visible bubbles came out from the line. It's definatley better but still not as flowing as the skimmer line. As it's a new line, it has been capped off which I removed when fitting the liner, so no sediment or anything else has got down there or blocking it. Any suggestions welcome but will purist.... May even try a dynorod type company to see if they can help!!

  15. #12
    Senior Member Rank = Hassai Mike Bass's Avatar
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    Quote Originally Posted by Mabbs View Post
    OK, done lots of bits on the pond today and spent some time trying to resolve the blockage/airlock. We have pushed a hose pipe down from the filter, probably a good 2 meters down the line and turned on hose. Can't really say it has improved the flow. Jumped in pond and removed bd cap. Pushed the hose pipe up about 2 meters and turned on tap. Again, hasn't really done anything. So at this point I put the pump on full throttle and kept opening and closing the gate valve. This has some success and some visible bubbles came out from the line. It's definatley better but still not as flowing as the skimmer line. As it's a new line, it has been capped off which I removed when fitting the liner, so no sediment or anything else has got down there or blocking it. Any suggestions welcome but will purist.... May even try a dynorod type company to see if they can help!!
    I have looked at your impressive build thread to try & get any ideas. Do you have any curves in the BD pipe work? If so are they swept 4” bends?

  16. #13
    Yes there are about 6 x 90 deg bends in the bd line, they are not swept. From the bottom drain, progress is all upwards towards the filter. There was one straight line about 1 meter long that was level and I am just wondering if that may have dropped down hill. This may cause an air lock in the previous bend, effectively up hill, if that makes sense!!

  17. #14
    Senior Member Rank = Mature Champion dbs's Avatar
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    I am no expert but have a sad feeling the 6 elbows are the cause of the poor flow, they create turbulence, swept bends should be used to keep flow at its maximum.

    I found this the other night whilst looking at other stuff, explains it well... YOUTUBE
    Last edited by dbs; 26-07-2020 at 09:09 PM.

  18. #15
    I have the same on the skimmer line as they are next to each other and the skimmer line is fine. The only difference is that there is a 3 meter straight run from the bd cap to where the bd line meets the skimmer line on the pond wall ?

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  20. #16
    Senior Member Rank = Hassai Mike Bass's Avatar
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    Quote Originally Posted by Mabbs View Post
    Yes there are about 6 x 90 deg bends in the bd line, they are not swept. From the bottom drain, progress is all upwards towards the filter. There was one straight line about 1 meter long that was level and I am just wondering if that may have dropped down hill. This may cause an air lock in the previous bend, effectively up hill, if that makes sense!!
    yes there could be an airlock If the bends twisted also the bends will slow down the flow to some extent.

  21. #17
    Senior Member Rank = Mature Champion dbs's Avatar
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    Quote Originally Posted by Mabbs View Post
    I have the same on the skimmer line as they are next to each other and the skimmer line is fine. The only difference is that there is a 3 meter straight run from the bd cap to where the bd line meets the skimmer line on the pond wall ?
    Hmmm well that blows my guess then

  22. #18
    Yes it's a bit frustrating. The fact that I have an Identical line running next to it with regards bends and run length, and that is fine, is confusing. At worst I will get a camera put down the line just out of curiosity, but I will have another go tomorrow to try and flush, what I think is an air lock out of the line??!!

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  24. #19
    Extreme Koi Member Rank = Adult Champion NickK-UK's Avatar
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    Quote Originally Posted by Mabbs View Post
    Yes there are about 6 x 90 deg bends in the bd line, they are not swept. From the bottom drain, progress is all upwards towards the filter. There was one straight line about 1 meter long that was level and I am just wondering if that may have dropped down hill. This may cause an air lock in the previous bend, effectively up hill, if that makes sense!!
    You could reverse the flow down the inlet by putting a pump sucking from the BD. Run at 20-30,000lph and it should clear any air at that rate.

    A 4" pipe is likely to have a max of 18,000lph, or 15,000 for most people in a gravity feed. The length of pipe and corners provide a natural constriction of flow unfortunately.

    I see that they are elbows and not swept - that would make a reduction from that 15,000 figure.

    You can hire drain cameras - it may help diagnose but I'm not sure if you could get around the elbow 90s.
    14000l, my mutts: Chargoi (2010), Doitsu (2022), Tancho (2022), Kujaku (2022), Hi Utusri (2022)

  25. #20
    Quote Originally Posted by NickK-UK View Post
    You could reverse the flow down the inlet by putting a pump sucking from the BD. Run at 20-30,000lph and it should clear any air at that rate.

    A 4" pipe is likely to have a max of 18,000lph, or 15,000 for most people in a gravity feed. The length of pipe and corners provide a natural constriction of flow unfortunately.

    I see that they are elbows and not swept - that would make a reduction from that 15,000 figure.

    You can hire drain cameras - it may help diagnose but I'm not sure if you could get around the elbow 90s.

    I think I will give your suggestion of using 20-30000 ltr/hr pump up the bd and back down the other way to see in that helps....... Need to fids some one who I can borrow a submersible one from!!

 

 
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