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Discussion Starter · #1 · (Edited)
Not sure if this should be in the DIY forum or in the Equipment forum, so if I guessed wrong, would a mod please move it?

Does a canister filter absolutely have to be completely below the tank? For the stand I want to build, Height is an issue. I don't think I have enough room to build a compartment for the tank and still have room for the filter underneath and still be able to maintain and access the filter, etc. So I wondered if this would work:



I could put the filter in a separate compartment, either next to the tank or behind the back wall of the tank so it's still not seen. That is, if it would work and not hurt the filter motor or prime, etc.

What do you think?
 

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Hmm...your diagram does not load for me but from what I understand placing a canister or anything with a motor below the tank actually creates extra load on it by forcing it to overcome the vertical distance (height) of the tubing rather than simply pumping to circulate.

So I would conclude that placing the pump on the same level should not only have no deleterious effects but might in fact ease the load and lengthen the lifespan of your motor.
 

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Discussion Starter · #3 ·
sorry about that. Apparantly if you link to an image in your email, you're the only one who can see it. Fixed it now by moving the picture to flickr.

That's a good point about the added lift putting more strain on the motor. the only experience I've had with canisters, the instructions tell you to put the canister under the tank, somewhat in the middle, then run the return to one back corner of the tank and the intake to the other back corner. I didn't know if or how it would affect the siphon.

If you've been able to run yours next to the tank, though, that's very encouraging.
 

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I see your diagram now.

I should have clarified that I was speaking theoretically and haven't actually done it. However, I know that a lot of people use those Tom Rapids Mini Canisters for Nano tanks and place them immediately beside their tanks so I know people have done it. But I would hesitate to conclude that the same principle would apply to the larger canisters (particularly if the instructions tell you to place it below the tank).

I will say also that you're probably right about the siphon being the issue to consider but I would still assume that if your inflow/outflow pipes are placed above the canister (which they will be since the tubes have to scale the side of the aquarium) that that should not be an issue.
 

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Some canister filters require a minimum head height. The XP is one of them.

You should do some research.
 

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Discussion Starter · #6 ·
Some canister filters require a minimum head height. The XP is one of them.

You should do some research.
yeah, that's what I'm trying to do here. When I try to google canister filter placement, I don't find much that's helpful. Now that you used the term "Head height", though, I can google that and see what I come up with since I've never heard that one before.
 

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As long as all of the canister is below the waterline, I don't see how it would make a difference. With the filter mounted higher, the return pump has less head to overcome, but this is counteracted by the decrease in pressure in the intake and the cansiter body, by virtue of the fact that the intake fall distance is shorter. So it's a wash.

Canisters are not designed to operate above the waterline, however.
 

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First to clear some misconceptions:

Canisters require to be below the water line. A canister is a closed loop system, meaning that the canister pump only has to move water against the friction in the tubing and media basket. It does not have to over-come gravity since the water is in a closed system. If you had a frictionless pipe, you could place your canister 50 feet below the tank and it would still work but since the tubing does create friction most canisters can only be 7 or so feet at max. To prove that gravity is not a factor all you have to do is turn off the canister. The water stops moving but does not drain, meaning the filter is only working against friction not gravity(which would drain the water if it was).

This is why canisters will not work when placed above the water line, they are no longer closed loop systems. The pumps in canisters are not powerful enough to draw water against gravity. If you were to place a running canister above the water line and turned the power off, the canister would drain showing that the pump is now working against gravity.

Looking at your diagram it looks like it will work but check to see if you have a minimum head height.
 

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yeah, that's what I'm trying to do here. When I try to google canister filter placement, I don't find much that's helpful. Now that you used the term "Head height", though, I can google that and see what I come up with since I've never heard that one before.
You may have to go to the particular website that has the instructions for the canister filters that you are looking at. In other words, the manufacturer's site.

I know that you can find this info on the XP site and Eheim's site. Look for their manuals.

Here you go.

On page 3 of the Eheim 2215/2217 manual has picture D. This shows that these filters need to be 10 cm below the water line. These are two of the filters that will work for your project.
http://eheim.com/base/eheim/pdf/en/anleitungen/afilter/2215_2217_classic.pdf

From what I remember, the XP's need to be something like 20" or more below the water line. Here is the instructional video for installation. I haven't looked at it.
http://www.rena.net/Products/Product.aspx?ProductID=346
 

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First to clear some misconceptions:

Canisters require to be below the water line. A canister is a closed loop system, meaning that the canister pump only has to move water against the friction in the tubing and media basket. It does not have to over-come gravity since the water is in a closed system. If you had a frictionless pipe, you could place your canister 50 feet below the tank and it would still work but since the tubing does create friction most canisters can only be 7 or so feet at max. To prove that gravity is not a factor all you have to do is turn off the canister. The water stops moving but does not drain, meaning the filter is only working against friction not gravity(which would drain the water if it was).
Great answer.
 

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Discussion Starter · #11 ·
Thanks for the links to the manuals and video, LeftC. And thanks to everyone that's weighed in on this. I'm learning a lot (which is one of the reasons I love this hobby so much).

The video says the head height is 2 feet for the XPs, so I will have to look at my meaurements/diagrams to see if that's possible in this setup. The whole display - 55 gallon tank, lights, roof above it, and the supports under it - comes to a whopping 38" high, so I may have to look for a different canister filter than an xp.

it's interesting to see what drives the decision on what to buy. It seems that the XPs and Eheims are the industry de facto standarad, but Eheim's are expensive, even on ebay, so they're kind of out. A used XP is cheaper, but the head height is too high so that may be out.

What's the general Consensus on the Fluval/Jegar canisters? are they too cheaply built to be worth it? I'll have to look into their minimum head heights and post my findings.
 

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Hmm...your diagram does not load for me but from what I understand placing a canister or anything with a motor below the tank actually creates extra load on it by forcing it to overcome the vertical distance (height) of the tubing rather than simply pumping to circulate.

So I would conclude that placing the pump on the same level should not only have no deleterious effects but might in fact ease the load and lengthen the lifespan of your motor.
I think the original question has already been answered sufficiently, but for information purposes, I've read that your theory is not totally correct. For reasons I don't know, upping the load on a water pump increases life expectancy. A pump loaded at 95% of it's max head will last longer than one at 50%.
 
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