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  1. #11
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    Incorrect, unless there no back pressure of air to press down on the water level from figure 2. If there is no air pressure present in figure 2 at the red line, THEN the water would go up as indicated in figure there. In reality it would go up further from figure 2, but not as high as figure 3. The only way for that to happen would be to create a vacuum, typically through suction, which is what happens when you use a pump at the top. You are causing a vacuum to PULL the water up from the red line in figure 2 to the red line in figure 3. That's why I said the pump is doing way more work than it should be doing.
    Last edited by Humblepie; 02-10-2012 at 4:18 PM.





  2. #12
    Junior Member tvsb's Avatar
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    Quote Originally Posted by Humblepie View Post
    Incorrect, unless there no back pressure of air to press down on the water level from figure 2. If there is no air pressure present in figure 2 at the red line, THEN the water would go up as indicated in figure there. In reality it would go up further from figure 2, but not as high as figure 3. The only way for that to happen would be to create a vacuum, typically through suction, which is what happens when you use a pump at the top. You are causing a vacuum to PULL the water up from the red line in figure 2 to the red line in figure 3. That's why I said the pump is doing way more work than it should be doing.

    Did you check the link that i give you ? communicating vessels ?
    there is everything about communicating vessels, that is old stuff ..
    On this filter pipe diametar (in/out) are much larger than diametar of in/out on pump, so in my filter are actually pressure "not underpressure". Pump do not suck the water in this case, pump actually pushes the water ahead, and new water coming to pump, everything has been said in the above pictures, description and link.



  3. #13
    Senior Member Goodcreature's Avatar
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    Actually, in figure 2, the red line wouldn't even have to be that low on the tube going into the filter for a siphon to start. As long as the overhead pressure pushing the water down on that side of vertex is more than that of the other side of the vertex (the side of the tube going into the aquarium), a siphon will start. Everything tvsb has said is right.

    I was making some plans to do a canister filter for my 55 gallon, and I was thinking along the lines of something like this. I'm already trying to build one of these for my shrimp jar. Very neat idea.
    Be reasonable. Do it my way.



  4. #14
    Junior Member tvsb's Avatar
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    Quote Originally Posted by Goodcreature View Post
    Actually, in figure 2, the red line wouldn't even have to be that low on the tube going into the filter for a siphon to start. As long as the overhead pressure pushing the water down on that side of vertex is more than that of the other side of the vertex (the side of the tube going into the aquarium), a siphon will start. Everything tvsb has said is right.

    I was making some plans to do a canister filter for my 55 gallon, and I was thinking along the lines of something like this. I'm already trying to build one of these for my shrimp jar. Very neat idea.
    You are right about the red line, i was hurry, thanks for correct me

    I was wondering when will someone who understands this, come here to support what I am talking.



  5. #15
    Senior Member vequalsir's Avatar
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    The design seems to be like a deconstructed fluval canister. I guess they don't know what they are doing either.

    The intake of the canister should go directly to the base of the can. Return pump should be at the top of the assembly to reduce the height of the head. This shortens the height the water has to be lifted by the pump on return and will reduce wear on the pump overall.

    Priming might be a bit difficult at first; however the valves he installed will allow you keep the pipes full during maintenance.

    I say nice build!
    Looking to meet Aquarist in the Cleveland Ohio area:
    Cleveland Aquarium Society



  6. #16
    Senior Member mott's Avatar
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    Not like the fluval cans at all...
    This diy can uses the same design just like the first canister ever built! the Eheim Classic, input to the bottom of the can up through the media to the top out to the pump.
    Been the same design for 40+ years! I think somebody from Eheim would have redesigned the classic if they found a flaw by now.
    BTW, that same canister has a reputation for lasting the longest out of any canister on the market!



  7. #17
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    Yeah I am afraid that humblepie really doesn't know what he is talking about. It's a closed loop. The water can enter anywhere in the canister you want. It will still flow through and the pump won't work any harder although you may bypass your filter media unless it is arranged properly.

    The only reason to have the inlet and outlet at the top is convenience. It makes disconnecting easier. If you actually look at a cross section of a canister filter you will see there is a pipe that extends from the top down to the bottom (underneath the baskets on units with baskets) which makes the inlet really at the bottom. It's just going through the canister first.

    In a closed loop the pump is not fighting gravity. But it is fighting friction in the lines and resistance through the media. Most units have the pump at the top for two reasons. Air bubbles rise which allows the pump to efficiently evacuate them from the system during priming, and debris won't settle into the impeller well over time. Marineland Magnums have the impellers at the bottom and they would often half fill with air over time and get carbon down into the impeller well which would damage the impellers.

    The only real issue I see with this DIY design are the brass fittings. Brass is a copper alloy and will leach copper into the aquarium over time. Aquariums are recirculating systems and the water has a very long dwell time so it's not like a home tap where the water passes through only once and doesn't have the time to pick up a significant amount of copper. Copper is lethal to invertebrates and chronic exposure causes liver damage to fish.

    Andy



  8. #18
    Junior Member tvsb's Avatar
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    Hello,
    thank you all for comments and coming here! I am so happy that i don't need to drow anything anymore
    Never really seen fluval or eheim filters, so i can not comment that.
    Pump is on top because of clean water, convenience... as we concluded
    These brass fittings are nickel-plated, except for nut. Release of copper is poor, and with weekly water change i think that the copper can not settle into the water in negligible quantity.
    Also, i think that the amount of copper that enters the tank through the microelements are far greater than would be deposited from this fittings.

    However, first i wanted to use plastic and i found only one version of plastic fitting, but they were not strong enough that could be used.(can be seen on one of the pictures, the black plastic fittings on the table)
    I wanted to be durable filter, works perfectly for 4 months now
    Last edited by tvsb; 02-15-2012 at 6:06 PM.



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