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  1. #1
    Senior Member Rank = Sansai GunHouseKoi's Avatar
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    Nexus 320 gravity - opinions/advice please regarding levels.

    Hi, had the filter up and running for several weeks now, but just the last few days, the level in the outer ring has gone down to about halfway......I have turned down the pump, but made no difference.

    The irritating thing is that I cannot figure out why this would be, bear in mind, for the last 4 weeks, it has been running fine, pump set at 66%and all the levels have been the same, IE, pond level........Now, how can one be lower, in a gravity system, surely they all find the same level? And why would it suddenly change after being constant for 4 weeks? Even setting a lower pump speed has not remedied it.

    what am I missing here?



  2. #2
    Senior Member Rank = Supreme Champion RS2OOO's Avatar
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    Do you have a blanket weed problem as this will slow the flow through the centre section into the outer section.

    If you turn your pump off completely does the outer chamber fill up to the same height as the inner chamber?

    Sent from my Pixel 2 using Tapatalk

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  4. #3
    Extreme Koi Member Rank = Kyusai Scamp's Avatar
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    Agree with RS, if when pump is off the water level of Nexus in inner chamber is level with level of pond, then thats fine. If the level drops hugely when pump is on, then either too fast flow or your there could be a blockage/restriction in your drain pipework. Do you have a bottom drain and 4" pipework? Have you tried purging the pipe to waste? Cheers

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  6. #4
    Senior Member Rank = Sansai GunHouseKoi's Avatar
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    Hi, no blanket weed, pond is clear as glass........yes, when the pump is off, the levels will stabilise. Have bottom drain and 4 inch. Its all new so should not be any build up that needs clearing and as I said, for the last 4 weeks using the same pump settings, all levels were stabilised the same. Then, without me changing anything, the outer nexus chamber level has dropped. This is the mysterious part for me, why? I have turned the pump down to 40% and its still low......did have it on 66% and it was fine for weeks, in fact I was playing around with settings and found initially that it really made no difference to the levels what setting the pump was on. Obviously, the higher the setting, the more frequently the pond volume gets turned over through the filter - it did not affect the levels. I cant see how a 1.5 m head of pressure with 4 inch pipework cannot keep up with 2 inch pumped return all of a sudden?

  7. #5
    Senior Member Rank = Supreme Champion RS2OOO's Avatar
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    There aren't really any further reasons why the outer chamber is so much lower then the inner chamber.

    Does it make any difference after you've thoroughly cleaned the inner section?

    If not, put the over flow pipe fully down, does it then equalise?

    If it does then the restriction is between the inner and outer section, if it doesn't equalise then the restriction is in your pipework.

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  9. #6
    Extreme Koi Member Rank = Kyusai Scamp's Avatar
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    Quote Originally Posted by GunHouseKoi View Post
    Hi, no blanket weed, pond is clear as glass........yes, when the pump is off, the levels will stabilise. Have bottom drain and 4 inch. Its all new so should not be any build up that needs clearing and as I said, for the last 4 weeks using the same pump settings, all levels were stabilised the same. Then, without me changing anything, the outer nexus chamber level has dropped. This is the mysterious part for me, why? I have turned the pump down to 40% and its still low......did have it on 66% and it was fine for weeks, in fact I was playing around with settings and found initially that it really made no difference to the levels what setting the pump was on. Obviously, the higher the setting, the more frequently the pond volume gets turned over through the filter - it did not affect the levels. I cant see how a 1.5 m head of pressure with 4 inch pipework cannot keep up with 2 inch pumped return all of a sudden?
    I agree its strange, thats why it sounds like a flow blockage. Are you running standard K1 in the outer chamber, or a mix of media/smaller types? The kiss points between the inner and outer chambers are slots. They can get blocked by media, that restricts flow. Could be worth using a long handled toilet brush and running it around the bottom of the outer chamber where it meets the inner chamber wall..it might free any media/other material if wedged down there.

    Or you could try back flushing the outer chamber to the inner chamber. To do this isolate Nexus in pipework. Insert centre pipe into Easy, then empty inner chamber to waste. Once empty remove the centre pipe and the water from the outer chamber will flush through to inner..Here you go:
    https://www.koijezirka.cz/files/file...structions.pdf

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    Senior Member Rank = Sansai GunHouseKoi's Avatar
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    Standard K1 that came with the unit. RS, what do you mean by "putting the overflow pipe fully down" ? will try whats suggested, thanks

    Just had a look at the instrcutions linked, thanks, however, I have the auto clean kit installed, so its a little more complex......can it be done with this installed? For example, I cant now manually drain the unit, as there is an automatic waste valve on the waste pipe that only opens when you run the cleaning sequence........ ,
    Last edited by GunHouseKoi; 28-05-2020 at 01:44 PM.

  12. #8
    Senior Member Rank = Sansai GunHouseKoi's Avatar
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    Ok, just home and found this




    What’s going on here????!!!


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  13. #9
    Extreme Koi Member Rank = Kyusai Scamp's Avatar
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    Hi you mean both levels down, or the eazy being off centre?

  14. #10
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    Are you using an automatic cleaning nexus? If so could it be cleaning much more often with this warm weather and all the algae and lowering your pond water level and therefore the level in the Nexus? Do you have a top up feed/trickle in the pond to compensate for the water loss flushed away?

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    Senior Member Rank = Sansai GunHouseKoi's Avatar
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    Hi, it’s on a 3 day clean cycle. And the pond level is pretty much unchanged ( maybe a few mm) The nexus is empty in the picture as I isolated it and started to empty it. I meant the off centre filter in the centre, why would it suddenly do that, surely it would need something to move it physically? How is attached? Does it come off easily? Can I do this?

    Looking at the linked backwash instructions, to me, they show the central mechanical filter drum bottom is tight up against the bottom of the central chamber.....mine is approx 150mm higher and seems to attached by some kind of flexible connection, although I can’t see, as I can’t get my head down there to look.
    I have emptied the central chamber with my pond vac and will check the kiss plates, but there was nothing obvious.

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  18. #12
    Senior Member Rank = Sansai GunHouseKoi's Avatar
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    I can’t see or feel the kiss plates......so can’t see if they are blocked....but currently, the central chamber is completely empty and the outer chamber 50% full.....should one not empty into the other and therefore the two of them maintain the same level ?

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  20. #13
    Extreme Koi Member Rank = Kyusai Scamp's Avatar
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    is water flowing from your pond into the central chamber? If not you have a block in your BD pipework - did you purge it as suggested? The central chamber should not be empty...

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  22. #14
    Senior Member Rank = Sansai GunHouseKoi's Avatar
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    Sorry to confuse you, it is empty as I isolated the nexus to investigate and drained all the water out so I could look at the suggested kiss plates etc......Bottom drain flows very well.

    In the event, I have filled it all back up and levels have remained constant in both chambers since. So not sure what caused it in the first place. Is the central filter supposed to be moveable like that? What about my query regarding the difference in the picture of the Nexus cutaway and how mine appears to be? If the water flow internally in the nexus is dependent on levels, if the inner filter chamber that had moved on mine, was higher, the that would mean that the central pipe that water goes through, down to the kiss plates and outer chamber, would also be higher and therefore not flowing water at a decent rate would it not? maybe that's why the levels were different?

    Are the back wash instructions superseded if you have the auto clean installed? For example I don't have any cleaning pipe?
    Cheers
    Last edited by GunHouseKoi; 29-05-2020 at 01:37 PM.

  23. #15
    Extreme Koi Member Rank = Kyusai Scamp's Avatar
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    The Easy section sits on the centre plastic moulded upward section of the Nexus inner chamber. There are stainless feet on the bottom of the stainless Eazy to facilitate this. The Easy should be central, not off to one side and located firmly. It is simple to remove, it just lifts off (once you disconnect the airline) if you need to remove. The cut away diagram shows the Nexus 310 style where the Easy located further down. Glad all seems to be ok. Perhaps when you drained it down it cleared the blockage, wherever it was..

  24. #16
    Senior Member Rank = Supreme Champion RS2OOO's Avatar
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    The overflow pipe I meant is the one you can just about see in the bottom right of your pic.

    Also yes, as scamp mentioned, the easy section doesn't look like it's fitted properly in the photo, could be an illusion or maybe you'd moved it out when draining it.

    Glad it sounds like you've sorted it now though.

    Other then the auto clean which I know nothing about, there's nothing that can go wrong with them really. They are pretty good filters on that front.

    Sent from my Pixel 2 using Tapatalk

 

 

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