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  1. #1
    Member Rank = Tosai richrich123's Avatar
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    Baffled by issue with gravity and pump??

    Hi,

    Wonder if anyone may have any ideas on this as I'm stumped.

    Recently put in a new pond which has a 4" BD and 4" skimmer line going into a drum and then into a moving bed bio unit

    Ive had it running the last few weeks with one 20,000 vario pump running back to 3 returns via the bio unit. All no problem, can run the pump happily from 30% minimum all the way to 100% / 20,000 lph with no issues.

    Tonight I have just connected up the shower to the second bio exit, run the second pump up (20,000 vario again) and after a minute heard it running dry. A quick check and bio unit was empty!

    Long story short, if I run pump one (returns) at 100% (20,000 litres) the water level doesn't budge in the drum/bio. If I turn it off and turn pump two (shower) on and run it at anything from 30% to 100% all fine.

    If I run both of them at 30% each, the water drops about an inch in drum/bio and of course starts triggering the drum to clean. Even if I leave it, it never returns back to normal running height, it stays about 1 inch lower than water level in drum and bio.

    As soon as I turn one or the other off, all returns back fine.

    I cant understand how 30% + 30% seems to cause a drop of an inch which never re balances as long as both are running at 30% . Yet run one or the other at full whack and its fine.

    Clearly something odd happening with 2x 30% that doesn't happen with 1 x 100%.

    Anyone have any ideas? I have tried turning one on, then a gap before the second, both at the same time etc but same outcome every time both run at 30% - Over an inch drop of level.

    A 20,000 running at 30% is 6,000 lph so 2 running is only drawing 12,000 which is no prblem for a 4" BD and 4" skimmer to supply (plus if I run the one pump at 20,000 it causes no issues. I must be missing something obvious??

    Cheers
    Rich



  2. #2
    Senior Member Rank = Adult Champion Twhitenosugar's Avatar
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    Hmmm. Odd.

    What drum do you have?

    Also just to double check, the first pump running your returns are after the bio unit I.e. attached to the outlet of the bio? Just checking as your message suggests the pump is before the bio, as you say 3 returns via the bio.

    Sent from my SM-A520F using Tapatalk
    13,000L fibreglassed raised pond with window

  3. #3
    Member Rank = Tosai richrich123's Avatar
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    Hiya, it’s a dracco solum 16 drum and dracco standard bio unit. The 2x 4” drum outlets go into the bio and the bio has 2 x 2” exits and I have 2 x aqua forte 20,000 vario pumps on each of the 2 bio exits, one to 3x returns and the other to the shower.

    Cheers.

  4. #4
    Senior Member Rank = Adult Champion Twhitenosugar's Avatar
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    Also how long are the pipe runs after your pump (not the shower one) and what diameter are they.

    It might be that you get large head loss if you have long pipe runs and/or lots of elbows. So your first pump might not be shifting anywhere near the 20,000l on 100% wattage. And the shower pump coming on could be enough to then take more than the drum can handle.

    But saying that, an inch drop in the water level in your bio doesn't sound like an issue. I'm pretty sure the water level in my bio is a fair bit lower than the pond level.

    But obviously it being drained dry is.

    Sent from my SM-A520F using Tapatalk
    13,000L fibreglassed raised pond with window

  5. #5
    Senior Member Rank = Adult Champion Twhitenosugar's Avatar
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    I've got the solum 16. And it's max rating is closer to 12 - 14k litres, I'd say.

    Sounds like your pumps are too powerful for your drum to me.

    But as I say if they are both on at 30% and your bio drops an inch and stays there, I can't see that as being a problem.

    Sent from my SM-A520F using Tapatalk
    13,000L fibreglassed raised pond with window

  6. #6
    Member Rank = Tosai richrich123's Avatar
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    Hi,

    What I don’t understand is how one pump can run at 100% ie 20,000 lph and it doesn’t effect the water level in drum and bio but run 2 at 30% each and it causes the level to drop an inch.

    It’s like 2 running at 30% is actually processing a lot more water than one at 100% which isn’t right.

    Putting aside what the drum is / recommended to run, the 2 pumps at 30% is 12,000 lph and given what a 4” bd can deliver, it shouldn’t be resulting in an inch drop of water level within seconds of both pumps starting (especially when one pump at 100% doesn’t have any efffect?

    The problem it is cause by dropping an inch is even with the drum clean, the float is now very close to horizontal and it would be triggering to clean every 5 mins
    Last edited by richrich123; 08-07-2020 at 09:49 PM.

  7. #7
    Have you tried swapping the pumps round?

    Maybe pump 1 is duff and isn’t actually pulling much at all, pump 2 is pukka and will shift loads of water.
    Maybe the return on pump 1 isn’t great but the return on pump 2 is fine.
    A 1” drain down isn’t a big issue and would be expected. With both running you’d probably get more.
    As others have said, even at half speed, 2x20k pumps is more than a drum that size could handle, my Synergy 35 can only just about do 2x20k pumps and that’s when the dirty side is clean, I’ve drained my lot on a couple of occasions so after a spot of twiddling I’m settled on both at about 60%.


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  9. #8
    Senior Member Rank = Adult Champion Twhitenosugar's Avatar
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    I had the same issue regarding the float switch being too high on my draco drum too. I personally think the stem that the float switch is attached to should be made longer (or the bracket that clamps it is lowered slightly).

    To get around the issue you have, I dropped the float switch initially so it was clamped by the very top of the stem. But then dropped it further and have lightly clamped the cable instead. It's been running like that since November and has been fine.

    Have a play about with the float switch, and find a level that works for your set up. I'm sure you'll be able to set it so both pumps are on low and the drum isn't cleaning too frequently.

    There's a thread about the Draco drum 16 under the product review section on here. Probably worth a read.

    Sent from my SM-A520F using Tapatalk
    13,000L fibreglassed raised pond with window

  10. #9
    Quote Originally Posted by Twhitenosugar View Post
    I've got the solum 16. And it's max rating is closer to 12 - 14k litres, I'd say.

    Sounds like your pumps are too powerful for your drum to me.

    But as I say if they are both on at 30% and your bio drops an inch and stays there, I can't see that as being a problem.

    Sent from my SM-A520F using Tapatalk
    I also have the Draco Solum 16 with the midi bio. It CANNOT handle 16000 litres an hour. Absolutely no way. As you’ve said I think 12-14k unless the mesh is swapped out to enable circa 24k.

    I cannot have my Oase 20000 in summer mode as it empties the bio and clean side of the drum so it has to be in winter mode which is 10k litres. I suck from both 2” bio ports using a manifold I made up out of a 90deg bend and Swept T as I noticed the media was getting sucked to one side of the bio - and that was only on 10k per hour with 150litres media and - 100lpm air pump! I don’t think this is enough.

    I’ve built my own shower today and I am going to run the pump on full, T it off from the pump with valves each side then one to the pond and the other to the shower. From the shower one 2” return to the pond and another 2” return back into the bio - this way I can be recirculating at a higher rate.

    OP - you could do the same arrangement as I’ve described with one pump that T’d off to your pond and shower. I wonder if the resistance on your existing return circuit is so much that you aren’t getting anywhere near 60% so we’ll under 12000lph. Your shower will have head but maybe very free flowing so running at not far off 30%.
    Scenario one - basically pump A could only be doing 10k LPH when at 100%.
    scenario two - pump A doing 5.5k LPH but pump B doing 5.5 LPH therefore 11k total.

    I’m disappointed with my Draco system as it’s a PITA to balance it all out and I wouldn’t get another one tbh. I don’t believe flow rates are anywhere near what they say.

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  12. #10
    Quote Originally Posted by Twhitenosugar View Post
    I had the same issue regarding the float switch being too high on my draco drum too. I personally think the stem that the float switch is attached to should be made longer (or the bracket that clamps it is lowered slightly).

    To get around the issue you have, I dropped the float switch initially so it was clamped by the very top of the stem. But then dropped it further and have lightly clamped the cable instead. It's been running like that since November and has been fine.

    Have a play about with the float switch, and find a level that works for your set up. I'm sure you'll be able to set it so both pumps are on low and the drum isn't cleaning too frequently.

    There's a thread about the Draco drum 16 under the product review section on here. Probably worth a read.

    Sent from my SM-A520F using Tapatalk
    Exactly the same on mine! The stem needs to be another inch longer. There are two brackets and I’m wondering about tapping the bottom one so I can use that to allow it to be lower.

    otherwise if float is too high it comes on constantly and then auto shuts off leaving the drum to block, bio to empty and pump to run dry. Like I’ve said before - not impressed by Draco at the moment.

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  14. #11
    Senior Member Rank = Adult Champion Twhitenosugar's Avatar
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    I agree with everything you've said there Dave.

    Im not against draco as such, but wish id gone for the Solum 25 instead. My pond is only 13,000l and told myself surely the 16 should be enough - at the time I thought the 25 would be excessive?

    But the reality is I'm right on the brink of what the drum can handle.

    I opted for a custom bio (jbr) rather than the draco bio. I, like you guys, wanted to add a shower but was concerned I'd be trying to pull too much through the drum.

    So my work around was to drop a jebao 10,000 vari pump into the bio itself and have the shower empty back into the bio too. Tbh it's worked out pretty well and saved me having to install tank connectors into the bio. Great for dwell time too. Although I appreciate you can't really do that with the draco midi.

    I like your idea re the manifold Dave. I might try that on my bd going into the drum i.e. so the bd feeds both inlets on the drum, and have the skimmer on a sieve.

    That way I'll have much better flow rates going through the drum and a sieve, rather than having the drum as a major bottle neck.

    Sent from my SM-A520F using Tapatalk
    Last edited by Twhitenosugar; 08-07-2020 at 11:44 PM.
    13,000L fibreglassed raised pond with window

  15. #12
    Excuse the mess but this is what I’ve knocked up today to get it going whilst running in winter mode. Plan to move it to the far left back corner and have one line straight into the riser bio chamber then run the other to the pond. Once sorted I’m going to build an outhouse around it to match the barn lap adjacent.

    E726348B-37C9-4462-89F4-E1B37F378296.jpg

    It’s really tight where I’ve got in so I’m playing with different things to get the right result. On the inlets to the drum I’ve got my 4” BD and on the other I’ve made up a pipe riser with a couple air stones in so try and remove any DOC. I’m trickling in so have now just got the 2”skimmer pipe fixed as an overflow pipe that’s going to go to my manhole nearby, it’s actually proved really effective over the last two days I’ve been trialling it and stops the pond water leaking down the sides of the pond. I did try to put an overflow using a 4”riser between BD and drum but it flooded everywhere and used to go up and down every couple of seconds due to the flow rate.
    Last edited by DiabloDave; 09-07-2020 at 12:11 AM.

  16. #13
    Senior Member Rank = Rokusai RipleyRich's Avatar
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    Quote Originally Posted by Twhitenosugar View Post
    Also how long are the pipe runs after your pump (not the shower one) and what diameter are they.

    It might be that you get large head loss if you have long pipe runs and/or lots of elbows. So your first pump might not be shifting anywhere near the 20,000l on 100% wattage. And the shower pump coming on could be enough to then take more than the drum can handle.

    But saying that, an inch drop in the water level in your bio doesn't sound like an issue. I'm pretty sure the water level in my bio is a fair bit lower than the pond level.

    But obviously it being drained dry is.

    Sent from my SM-A520F using Tapatalk
    This is exactly the problem.

    Forget the pump rating and the % power, because that is all it is, % power. Its is not % flow.

    There will be a pump curve that shows flow versus power against head loss. The pumps rating (lets say 20000 lph) will be rated at 100% power against a nominal head loss. Usually 2m.

    However, your pipe, valves, fittings, UV`s etc all add head loss due to resistance and reduce flow capability.
    Consider an outside tap, fill a bucket from the tap and it takes maybe 10 seconds.
    Now connect your 25m hosepipe and the bucket takes 40 seconds to to fill.
    That is due to resistance.

    Have a look at this as it will give you an idea of the resistance of your 2 systems. By comparing the tow, it will help you understand the difference between them.

    https://www.plasticpipeshop.co.uk/Fl...Ff8FroCwCV0tqQ

    Ideally you need to get hold of a pump curve. You say the 20000 pump at 30% gives 6000 lph. But that will be at 2m head (probably) If you use the calculator above to get a better idea of your head loss, you will find that you probably have significantly more head loss. Unfortunately flow and head loss is not a linear scale either, double the head loss doesn`t mean half the flow, it has much more impact than that.

    Then we come to the more important issue of the bottom drain and skimmer.
    You again need to calculate the head loss for these. Water will always take the path of least resistance, which invariably means that you may not be getting the flow you require from one or the other.

    What is obvious, is that with both pumps running, the pipes from the bottom drain and skimmer cannot deliver that flow rate to the filter and consequently you run dry.

    Next question, what is the pond volume?
    20000 lph is c4000 gallons ph
    40000 lph is c8000 gallons ph

    You only need to turn your pond volume over every 1.5 - 2 hours.

    I am guessing that with one bottom drain, your pond is less than 4000 gallons?
    If that is the case, it seems like you are trying to turn it over twice an hour?

    Without the full information or understanding further about what you are trying to achieve, the solution would be 2 x 10000 pumps, or fit one 20000 pump and tee the returns with a valve on each so that you can balance the flow to each return.

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  18. #14
    Quote Originally Posted by RipleyRich View Post

    What is obvious, is that with both pumps running, the pipes from the bottom drain and skimmer cannot deliver that flow rate to the filter and consequently you run dry.
    Everything in your post is good - except the above; it’s the drum that’s the issue not the supplying pipe work. The drum can only handle an absolute max of 16k LPH (manufacturer says but I believe it’s lower from my own experience). I can guarantee that the dirty side of the drum is at the right level but the clean side is almost drained.

  19. #15
    Senior Member Rank = Rokusai RipleyRich's Avatar
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    Quote Originally Posted by DiabloDave View Post
    Everything in your post is good - except the above; it’s the drum that’s the issue not the supplying pipe work. The drum can only handle an absolute max of 16k LPH (manufacturer says but I believe it’s lower from my own experience). I can guarantee that the dirty side of the drum is at the right level but the clean side is almost drained.
    I have no experience of that drum so completely take your word for that.

    Does it have a bypass overflow? My Oase does.
    Or can the screens be removed easily?

    I ask that because at the moment, we have no idea what flow rate he is getting from his pumps.
    Looking at the pictures, the runs are short, so I would imagine head loss isn`t too high, although there is a lot of fittings.
    By bypassing the drum resistance, it will confirm or eliminate any restriction problem with the bottom drain and skimmer.
    I still have a gut feeling that those 2 pumps are overwhelming the capacity of the 2 inlets. But again, that is with no knowledge of that particular drum.

  20. #16
    Extreme Koi Member Rank = Gosai koicarpus's Avatar
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    You need to buy some flow meters from Absolute koi. As said above pumps % power doesn't reflect on flow.

    https://absolute-koi.com/cat1432.html

  21. #17
    Quote Originally Posted by RipleyRich View Post
    I have no experience of that drum so completely take your word for that.

    Does it have a bypass overflow? My Oase does.
    Or can the screens be removed easily?

    I ask that because at the moment, we have no idea what flow rate he is getting from his pumps.
    Looking at the pictures, the runs are short, so I would imagine head loss isn`t too high, although there is a lot of fittings.
    By bypassing the drum resistance, it will confirm or eliminate any restriction problem with the bottom drain and skimmer.
    I still have a gut feeling that those 2 pumps are overwhelming the capacity of the 2 inlets. But again, that is with no knowledge of that particular drum.
    Yes there are two sections that can be removed to achieve this. Haven’t tried to remove the screen tbh.

  22. #18
    Quote Originally Posted by koicarpus View Post
    You need to buy some flow meters from Absolute koi. As said above pumps % power doesn't reflect on flow.

    https://absolute-koi.com/cat1432.html
    I really don’t see the point in spending hundreds of pounds to do this. The pumps are too powerful for the drum. It’s as simple as that! OP can always do a bucket test and time how long to fill them work out LPH - cost 99p for a new clean bucket.

  23. #19
    Extreme Koi Member Rank = Gosai koicarpus's Avatar
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    Quote Originally Posted by DiabloDave View Post
    I really don’t see the point in spending hundreds of pounds to do this. The pumps are too powerful for the drum. It’s as simple as that! OP can always do a bucket test and time how long to fill them work out LPH - cost 99p for a new clean bucket.
    Calm down Dave, It's obvious that the pumps are too powerful. Just saying that these flow meters are great, can help with set up, and help alleviate any doubt with flow from pumps
    Plus it's almost impossible to do a bucket test for a lot of people, including myself

  24. #20
    Extreme Koi Member Rank = Supreme Champion Frimley Koi keeper's Avatar
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    Could it not be as simple as with 1 pump pushing water through 1 pipe system there is x amount of water being pumped round but with a second pump pushing water through a second pipe system there is potentially more water being spread around more pipe work etc so even though you are running the 2 pumps at a lower combined flow rate you are in reality pushing more water round more pipe work?

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