Canister filter question!

[norg]

Originally Posted by Aponogeton

Why is your jebo filter garbage?

I just purchased a short and stout jebo 835, for 80 dollars, it was one of the few that would fit under my very short stand for my 60 gallon. First Canister filter.

Jebao yes. It is very finicky when getting it to seal. It likes to leak and has pretty low GPH flow through it. Its a pain to get it to seal everytime and sliced my hand open pretty good after I punched it in frustration. Overall I hate it.

[Aquaticfan]

Some things to think about from an experinced Canister filter user.......... Ive been using these things over my last 30 plus years in the hobby.... Some issues I see with your plan.

The INTAKE side of the filter opperates 100% off of gravity. Not suction not pumping pressure. But purely from gravity flow down the tube and into the filter. If you run it level you will have very very low to zero intake flow coming from the tank to keep the canister filled. While you will have less head pressure to run the pump on the outlet side, you wont be able to feed the pump due to the reduced to no flow.

Next..... Your putting this in a dresser and below its clothes you wear? Murphys law on canister filters. Isnt If it will leak. Its WHEN it will leak. There are 2 types of canister filter owners. Those that have had leaks and those that will. I see disaster and not so happy. The only good thing is your intake will be so poor it may not be able to leak a whole lot. BUT id bet its enough to ruin your day.

Next the amount of hose.. The length and the shape/position the hoses are in can and will effect flow rates. In the first pic you have I see the hoses are long and have some loops and curves. This slows flow and creates issues for air pockets when trying to prime. When in opperation the flow rate will go down. Most all manufactures recommend the shortest hoses you can get away with and recommend trimming them. They also recommend direct gravity flow. The pump in a canister filter is a pusher not a puller. So the effect of gravity flow also helps the water flow down to the bottom and up through all the trays and through the media where it reaches the pump in the head of the unit.

Purging at the same level as the tank will be more difficult.

[AndreyT]

Originally Posted by accordztech

I think you should consider that most canister filters work with gravity in which the filter has to be below the tank so that a proper syphon to deliver the water to the filter and the impeller pump can push it directly to the tank. If the filter is level to the tank in the dresser it may not funtion properly.

Absolutely not. That would be true for wet-dry filters. It does not apply to canister filters at all.

For a canister filter, gravity plays no role whatsoever. Canister filter is a sealed system with two siphons that precisely counterbalance each other. Regardless of how you place your canister relative to the tank, the system will work (as long as it remains sealed, of course). The filter's motor will not notice any difference, regardless of whether the canister is above or below the tank.

Now, to the original poster: Using longer tubes might produce additional "drag" in the tubes, i.e. the pump motor might have to spend slightly more effort in order to overcome the viscous friction in the tubes. However, 4 feet is not that far. Moreover, Eheim filters typically come with 8 feet of tubing, meaning that 4 feet of tank-to-canister distance is the standard distance for these filters. As long as your tubes are relatively straight (no knots, tight loops or compressed segments), you should be perfectly OK.

[AndreyT]

Originally Posted by Aquaticfan

The INTAKE side of the filter opperates 100% off of gravity. Not suction not pumping pressure. But purely from gravity flow down the tube and into the filter. If you run it level you will have very very low to zero intake flow coming from the tank to keep the canister filled. While you will have less head pressure to run the pump on the outlet side, you wont be able to feed the pump due to the reduced to no flow.

That's incorrect.

In any canister filter, the weight of the column of water in the intake tube is always precisely counterbalanced by the the weight of the column of water in the return tube. For this reason, the net effect of water weight in the tubes is always precisely and exactly zero. I.e. gravity plays no role in moving the water through the filter whatsoever.

Canister filters are not "fed by gravity", as it is often incorrectly believed. Wet-dry filters are fed by gravity, canister filters are not. This is the defining difference between open (wet-dry filters) and sealed (canister) filters. Canister filters, by design, do not require "feeding" at all. They are based on the idea of circulating continuous volume of "weightless" water. From the principle of operation point of view, canister filters do not have "intake side" or "return side": they are perfectly symmetrical in that regard. Speaking informally, both sides of canister filter always provide exactly the same "intake pressures", which meet inside the canister and cancel each other.

This is actually the fundamental principle that justifies the very existence of canister filters. Since gravity and weight of the water plays no role at all (the water in this system is effectively "weightless"), the pumps in canister filters does not have to "lift" the water. It only has to push the water through the media. Canister filters were invented specifically to take advantage of this principle.

As long as the system is filled with water and sealed, it can be placed below the tank, above the tank, next to the tank - anywhere. The filter itself and will not be able to feel any difference. The pump load will remain constant. This is just school physics.

P.S. The reason canister filters have height-difference limitation is not the pump load, but rather seal strength. The lower you place the canister - the greater the water pressure inside the canister becomes. If the canister is placed too low below the tank, the seals will begin leaking.

[mott]

Ah, but gravity does matter with canisters!
Try priming a can that is above or at tank level... Its a pita!

[AndreyT]

Originally Posted by mott

Ah, but gravity does matter with canisters!
Try priming a can that is above or at tank level... Its a pita!

As I said above, the "gravity doesn't matter" statement refers to the fact that the two siphons (intake and return tubes) precisely cancel each other when completely filled with water. I.e. gravity doesn't matter when the system is completely filled.

For example, if you unplug the pump in a filled and operational canister filter, the water will just stop. It won't flow anywhere. (Compare that to a truly gravity-fed system: a wet-dry filter. If you unplug the pump, the intake siphon will continue to feed water, eventually overflowing the filter.)

When the canister filter is empty and you just begin to prime it, then, of course, gravity does matter.

If the canister is located below the water level in the tank, then it can basically prime itself - you just have to give it a few pumps to pull the water over the level of the tank. The intake siphon will do the rest (although the hand pump might do it faster).

If the canister is located above the water level in the tank, then, as you correctly noted, you will have to keep pumping pretty hard until you fill the whole canister and the return tube.

[Aquaticfan]

Originally Posted by AndreyT

That's incorrect.

Ummm No its not incorrect, Physics is still physics. Canisters work on a gravity fed siphon. A canister filter relies on gravity to feed and prime the filter to fill it with water. With out it you cant get it filled with water. The pump does not create a vacuum - if it did, the canister would be capable of self priming. The filter doesnt use internal equalization to create flow. All it use the self equalization for is getting the water to the medium and to the pump.

Try this experiment.

Stand on a ladder or chair above your tank. Using a hose try to suck on the hose to create a syphon and pull water out of the tank. You can suck on the end of the hose and you might get the water to go up the hose while your sucking so hard your about fall over. BUT stop the suction and what happens. The water will run right back down the tube and back into the tank. Why.....?? No gravity to pull it down the tube to start the syphon effect. Do that over the side of the tank and you can pull the water right out of the tank. pull it back over the level of the tank and its no longer syphoning. So yes it takes gravity to feed a syphon. Thus a canister needs that to even fill the filter up to create equalization inside and gravity must be constat to keep a syphon happning.

Originally Posted by AndreyT

In any canister filter, the weight of the column of water in the intake tube is always precisely counterbalanced by the the weight of the column of water in the return tube. For this reason, the net effect of water weight in the tubes is always precisely and exactly zero. I.e. gravity plays no role in moving the water through the filter whatsoever.

If this was the case then a pump wouldnt even be needed all one would need to do is create a syphon and it would circulate. It takes the weight of the water falling (this is caused by gravity as weight is a form of gravity and its pull on things) through the tube on the intake to create the syphon thus filling the canister What happens if you get an air bubble in the intake tube but the canisters full? You get a canister filter that doesnt flow. How does the syphon keep flowing? Falling water through the tube continously filling the filter so it can reach the pump. Raise the canister above the tank and the syphon slows to a halt. Why.. Gravity has less effect. Resistance is higher and cretaes a flow restriction on the intake. Volume in is not equal to volume out. As mentioned before Canister are unable to pump/create vacuum inside a canister to keep a syphon or start a syphon. They are PUSH pumps only. There is a reason why manufactures of canister tell you they need to be placed lower below the tanks for a reason.

Originally Posted by AndreyT

Canister filters are not "fed by gravity", as it is often incorrectly believed. Wet-dry filters are fed by gravity, canister filters are not. This is the defining difference between open (wet-dry filters) and sealed (canister) filters. Canister filters, by design, do not require "feeding" at all. They are based on the idea of circulating continuous volume of "weightless" water. From the principle of operation point of view, canister filters do not have "intake side" or "return side": they are perfectly symmetrical in that regard. Speaking informally, both sides of canister filter always provide exactly the same "intake pressures", which meet inside the canister and cancel each other.

BOTH canisters and wet drys are fed by gravity and syphon effect. The only difference is the forces of atmospheric pressures between the two as the wet dry is exposed to such pressures and canisters are not. Canister filters are basicly a controled leak. Your creating a leak by means of gravity to flow down an intake tube fill a fliter and then get it to a pump that pushes it up a outlet. All the while following the least pasth of resistance. The leak being the path of least resistance.. Aka Intake leaking flow into the canister via gravity and output being push via pump as long as you dont excedee the head pressure.

Originally Posted by AndreyT

This is actually the fundamental principle that justifies the very existence of canister filters. Since gravity and weight of the water plays no role at all (the water in this system is effectively "weightless"), the pumps in canister filters does not have to "lift" the water. It only has to push the water through the media. Canister filters were invented specifically to take advantage of this principle.

Lets look at the MAJORITY of designs of canister.. Where is the pump located? Before or after the filter media? MOST ALL if not ALL pumps on canisters are AFTER the media. The filter brings in the water from the intake side via siphon flow caused by gravity. THEN it flows into the filter and goes to the bottom and fills the filter from the bottom up. Going through the Media trays from bottom to top. Its this way by design for 2 reasons. Using this method allows us to push out the air in the canister easier thus easier filling with water. It also allows for a Smaller pump to be used to get the job done if the pump is in the top of the filter at the outlet fitting as it then only has to force the water up the outlet hose. So a pump NEVER pushes the water through the media. It only pushes the water out the outlet hose. How does the water manage to get to the canister and to the bottom of the filter and through the media to reach the pump to allow the pump to do its job pumping it through a smaller hose back into the tank? Gravity and the path of least resistance. Whne using a sealed canister its forced in that direction of least resistance.

Originally Posted by AndreyT

As long as the system is filled with water and sealed, it can be placed below the tank, above the tank, next to the tank - anywhere. The filter itself and will not be able to feel any difference. The pump load will remain constant. This is just school physics.

Really? then why do canister manufactures tell you specifically placement of a canister needs to be below. Not next to, not above, not even with. Pump loads will NOT remain constant. If you change head pressure on any given pump a pump with lower head pressure will pump more. BUT its also proven that a syphon can not work if it is above or to equal with its souce. This is school physics. Its also proven the pump does not create a vacuum. If it did it would prime itself.

Originally Posted by AndreyT

P.S. The reason canister filters have height-difference limitation is not the pump load, but rather seal strength. The lower you place the canister - the greater the water pressure inside the canister becomes. If the canister is placed too low below the tank, the seals will begin leaking.

Sorry this description is just silly and makes no sense. A canister system is NOT a 100% sealed system. It has a inlet and an outlet. Pressure should NEVER build high enough to create a leak at a seal. Why? again.. Due to having a outlet in the filter. The reason for height limitations for the canister is the head pressure it applies on the pump trying to push the water up the hose. If it gets to high it will have to much head pressure and reduce the flow greatly or to nothing. Has nothing to do with causing a seal in the filter to leak. Remember Physics about water.... It follows the path of least resistance. The canister is it self a sealed unit except for the inlet and outlet. If you increase the resistance of the water with a higher head pressure you dont cause a leak. you just create zero flow due to the amount of head pressure fighting the waters abillity to return to the tank. At this point you dont have a syphon anymore you have zero flow out. Its just sitting stationary whith a pump running doing really nothing. Has ZERO to do with creating a seal to leak.



I know several Fluid Engineers and real world people that would disagree with your post on how it works. Gravity is involved. Does a syphon exist in zero gravity? I dont believe so..

http://en.wikipedia.org/wiki/Siphon

Canister filters and wet drys all work off of syphon effects, as you state yourself. (were not talking on back mounted filters) Syphons are the results of gravity.

[norg]

Originally Posted by AndreyT

That's incorrect.

In any canister filter, the weight of the column of water in the intake tube is always precisely counterbalanced by the the weight of the column of water in the return tube. For this reason, the net effect of water weight in the tubes is always precisely and exactly zero. I.e. gravity plays no role in moving the water through the filter whatsoever.

Canister filters are not "fed by gravity", as it is often incorrectly believed. Wet-dry filters are fed by gravity, canister filters are not. This is the defining difference between open (wet-dry filters) and sealed (canister) filters. Canister filters, by design, do not require "feeding" at all. They are based on the idea of circulating continuous volume of "weightless" water. From the principle of operation point of view, canister filters do not have "intake side" or "return side": they are perfectly symmetrical in that regard. Speaking informally, both sides of canister filter always provide exactly the same "intake pressures", which meet inside the canister and cancel each other.

This is actually the fundamental principle that justifies the very existence of canister filters. Since gravity and weight of the water plays no role at all (the water in this system is effectively "weightless"), the pumps in canister filters does not have to "lift" the water. It only has to push the water through the media. Canister filters were invented specifically to take advantage of this principle.

As long as the system is filled with water and sealed, it can be placed below the tank, above the tank, next to the tank - anywhere. The filter itself and will not be able to feel any difference. The pump load will remain constant. This is just school physics.

P.S. The reason canister filters have height-difference limitation is not the pump load, but rather seal strength. The lower you place the canister - the greater the water pressure inside the canister becomes. If the canister is placed too low below the tank, the seals will begin leaking.

I appreciate the feedback this thread is getting. I didnt expect it to turn into a debate, but hey thats cool too. lol I was under the assumption that the information above was correct, I was simply double checking before I bought anything. I have more than a couple years of aquarium experience under my belt. Most of it is with SPS reefing though, I figured the canister filter design would be similar to the idea of a closed loop design for creating flow in an aquarium. Meaning the gravity feed to the pump negates the head the pump pushes. However this obviously means this pump actively pulls water into the filter and through the canister filter, if the filter itself is level with the tank. My complete and total POS Jebao filter works this way. I figured most canister filters were this way. But then again I have very little experience with these filters. As an experiment I held my current POS filter level with the tank and it continued to run the exact same. Unplugged it and plugged it back in and had the same results.

[AndreyT]

Originally Posted by Aquaticfan

Ummm No its not incorrect, Physics is still physics.

Precisely. Physics is still physics.

Originally Posted by Aquaticfan

Canisters work on a gravity fed siphon.

No. Canister filter has two siphons leading into it, which precisely cancel each other.

Originally Posted by Aquaticfan

A canister filter relies on gravity to feed and prime the filter to fill it with water. ... The pump does not create a vacuum - if it did, the canister would be capable of self priming. ...

Try this experiment.

Stand on a ladder or chair above your tank. Using a hose try to suck on the hose to create a syphon and pull water out of the tank....

This is all correct, but completely irrelevant. What I said before explicitly applies to an already primed filter, i.e. a filter whose canister is filled with water, both tubes are filled with water and the tube ends are submerged in the tank. I though I made it clear.

Originally Posted by Aquaticfan

If this was the case then a pump wouldnt even be needed all one would need to do is create a syphon and it would circulate.

No, you got it completely backwards. What you are saying (i.e. your claim that canister filter is gravity-fed) means that the pump is not needed. A gravity-fed system would only need gravity to work. I.e. if canister filter were a gravity-fed system, it would work as Perpetuum Mobile without any pump.

The reason canister filter is not a Perpetuum Mobile is exactly what I said above: the siphon effect from the intake tube exactly and precisely cancels the siphon effect of the return tube. The net effect is zero. This is why water will not move by itself through the filter. This is why you need a pump is a canister filter.

Originally Posted by Aquaticfan

It takes the weight of the water falling (this is caused by gravity as weight is a form of gravity and its pull on things) through the tube on the intake to create the syphon thus filling the canister

Again, this is only true for priming the filter. This is completely irrelevant to the operation of already primed filter.

Originally Posted by Aquaticfan

What happens if you get an air bubble in the intake tube but the canisters full? You get a canister filter that doesnt flow.

I'm not sure what you mean here. No, a mere bubble in the intake tube will not stop the filter. In order to stop the filter you need a quite large bubble in the intake tube. When you remove water form the intake tube, you create a disbalance between intake- and return-side siphons - the return siphon produces greater back-pressure that intake siphon. With large bubbles this disbalance might get large enough to overpower the pump. But a mere break in the intake water column (a bubble) will not be enough to achieve that. How large that bubble will need to be depends on the "pumping" power of the pump. It will vary from filter to filter.

Originally Posted by Aquaticfan

How does the syphon keep flowing? Falling water through the tube continously filling the filter so it can reach the pump.

I'm not sure what the point of this is, but anyway:

Pump has absolutely nothing do to with siphon operation. The water falls down through the long output end of the siphon. As long as the upper end of the siphon remains submerged, atmospheric pressure will force the water from the tank into the upper end of the siphon, thus ensuring continuous operation of the siphon.

Originally Posted by Aquaticfan

Raise the canister above the tank and the syphon slows to a halt.

False. This will not halt the flow. This will simply reverse the flow in the siphon (as long as the upper end of the siphon is submerged).

The only way to the flow in a siphon is to make sure water levels on both sides are equal.

If the water levels are unequal, the siphon will always flow from the higher level to the lower level (again, assuming that the upper end remains submerged).

Originally Posted by Aquaticfan

Why.. Gravity has less effect. Resistance is higher and cretaes a flow restriction on the intake. Volume in is not equal to volume out.

Sorry, this just makes no sense to me.

Originally Posted by Aquaticfan

As mentioned before Canister are unable to pump/create vacuum inside a canister to keep a syphon or start a syphon.

Again, absolutely irrelevant remarks that only apply to an empty (i.e. non-primed) canister filter. What they are doing here is not clear to me.

Originally Posted by Aquaticfan

They are PUSH pumps only. There is a reason why manufactures of canister tell you they need to be placed lower below the tanks for a reason.

That's false. One reason to place a canister below the tank is to ensure that it doesn't get siphoned out during water changes. If you place canister above the tank, then when you expose the return (or intake) tube during tank water changes, the water will get siphoned out of the tubes (and possibly out of the canister, depending on the design). Also the filter will have to be re-primed afterwards. To avoid this it is recommended to place the canister below or next to the tank, but not above it.

There might be other reasons, tied to the design of the canister, but none of them are relevant to the basic principle of operation of the filter.

Originally Posted by Aquaticfan

BOTH canisters and wet drys are fed by gravity and syphon effect.

False. Only wet-dry are fed by gravity. Which is rather obvious from the fact that wet-dry filter continues to be fed even if you unplug the pump. Meanwhile, canister simply stops if you unplug it.

Originally Posted by Aquaticfan

The only difference is the forces of atmospheric pressures between the two as the wet dry is exposed to such pressures and canisters are not.

That's false and actually self-contradictory. You can't have siphon effect without atmospheric pressure. It is atmospheric pressure that makes water rise through the ascending leg of the siphon. Atmospheric pressure always acts on the tank water. There's no way to "hide" from it.

Originally Posted by Aquaticfan

Canister filters are basicly a controled leak. Your creating a leak by means of gravity to flow down an intake tube fill a fliter and then get it to a pump that pushes it up a outlet.

That's exactly what wet-dry filter is: a controlled leak.

This is absolutely not true for canister filter. Canister filter is not a leak at all. This is, again, the fundamental principle that justifies the very existence of canister filters.

If you ever inspected a wet-dry filter, you should know that they use a significantly more powerful pump than canister filters. This is exactly because in wet-dry filter the pump has to lift water back into the tank. Canister filters, meanwhile, use relatively small impeller pumps. The reason canister filters can get away with such tiny pumps is specifically that these pumps don't have to lift water into the tank. All the canister pump has to do is to make "weightless" water circulate through the tubes.

Originally Posted by Aquaticfan

Lets look at the MAJORITY of designs of canister.. Where is the pump located? Before or after the filter media? MOST ALL if not ALL pumps on canisters are AFTER the media.

It is completely inconsequential where the pump is located in the canister filter. It can be located anywhere in the water path. The only reason it is located after the media is to protect the impeller from possible debris, i.e. to put the impeller into already filtered water.

Originally Posted by Aquaticfan

Using this method allows us to push out the air in the canister easier thus easier filling with water. It also allows for a Smaller pump to be used to get the job done if the pump is in the top of the filter at the outlet fitting as it then only has to force the water up the outlet hose. So a pump NEVER pushes the water through the media. It only pushes the water out the outlet hose.

Sorry, that just makes no sense. Regardless where the pump is located, one way or another it will always have to perform work of forcing the water through the media. There's just no way around it. Otherwise, it would simply magically defy all fundamental laws of physics. The work required for pushing water through can't simply come out of nowhere.

I will not comment further, since the rest is just getting repetitive.

Originally Posted by Aquaticfan

I know several Fluid Engineers

I suggest you contact them and have them explain it to you.

[AndreyT]

Originally Posted by norg

I figured the canister filter design would be similar to the idea of a closed loop design for creating flow in an aquarium. Meaning the gravity feed to the pump negates the head the pump pushes.

Exactly! That is a very precise and concise description of the principle of operation of canister filter.

Originally Posted by norg

However this obviously means this pump actively pulls water into the filter and through the canister filter, if the filter itself is level with the tank.

I don't see how. As long as you have two tubes, fully and continuously filled with water and submerged into the water at both ends (tank end and canister end), the system remains a closed loop with two siphons precisely negating each other. You can place it absolutely anywhere: nothing will really change. I.e. the pump never has to actively pull water from the tank or push it to the tank. All the pump has to do is to "encourage" the water to circulate ("encourage" it well enough to make sure it flows through the media).

Originally Posted by norg

My complete and total POS Jebao filter works this way. I figured most canister filters were this way. But then again I have very little experience with these filters. As an experiment I held my current POS filter level with the tank and it continued to run the exact same. Unplugged it and plugged it back in and had the same results.

As it should. The only concern I have here is that in some filter designs the canister end(s) of the tube(s) might not be reliably submerged into the water (if there's a lot of stray air at the top of the canister). Such filters might not guarantee reliable "above the tank" operation. This would be another reason for filter manufacturers to require installation below the tank.

But if the canister water level is just slightly below the tank water level, the filter should work perfectly.

[Bandit1200]

Go AndreyT!!!

+11 to the above. I think that's what I said originally.

[TheDrake]

AndreyT is 100% correct: as long as the inlet and outlet are underwater in the tank, gravity has no effect on the operation of a primed pump. In that case, the pump is only working to overcome the resistance of the hoses, which will be greater the longer the hoses. Now, if you raised the opening of the outlet hose above the surface of the water, all bets are off: now the pump does additional work to return the water against gravity. I've seen this on plenty of occasions with a small pump trying to get water up to a higher tank. If the pump is only strong enough to make it up to the tank but not over the lip, you get no net flow. But if you run the hose up over the lip, under the water, and suck out the air…bingo=flow. Not everyone has the equipment to measure the output of a pump, but anyone with a small powerhead and a bucket can demonstrate this reality for themselves.

[Aponogeton]

Wow, a lot of reading.

Anyone know why my filter has a much larger intake tube than output tube.

My filter is a jebo and so far I've been happy with it and it has had zero leaks and zero sealing issues. I put a small film of petroleum jelly on everything and I lube the pins in the clamps so they don't wear out as easily as well as the o-rings. I would recommend it but don't get the clear one, I heard people having cracking problems with the plastic.

[brainwavepc.com]

all this arguing and speculation.... put your current filter on a chair or something at the height you want and see if it works, problem solved....